Home > Articles > Programming

The Failure of the GPL

David Chisnall casts a critical eye over the GNU General Public License (GPL) and asks whether it's done more harm than good for the Free Software movement.
Like this article? We recommend

In 1985, the Free Software Foundation (FSF) was formed to promote software freedom, as defined by these four freedoms:

  1. The freedom to run the program, for any purpose.

  2. The freedom to study how the program works, and adapt it to your needs.

  3. The freedom to redistribute copies so you can help your neighbor.

  4. The freedom to improve the program, and release your improvements (and modified versions in general) to the public, so that the whole community benefits.

One of the tools used to achieve this goal is the GNU General Public License (GPL). Looking back, has the GPL been a help, or a hindrance? And will it continue to be a help or hindrance in the future?

A GPL Success Story

The FSF website points out a specific instance of the GPL forcing a company to open its source. The company in this example was NeXT (now Apple), and the source code was the Objective-C front end for the GNU Compiler Collection (GCC). But what really happened?

When NeXT purchased the rights to Objective-C, it inherited two pieces of technology. One was a preprocessor—a fairly simple program that turned Objective-C into pure C. The other was a runtime library that handled all of the dynamic lookups, module loading, and other bits required for a complete Objective-C environment. The preprocessor approach had some limitations, not least of which was difficulty in debugging, so NeXT decided to move the preprocessor into the compiler.

The C compiler in use at the time was GCC, which was released under the GPL. To avoid the restrictions of this code, NeXT provided its front end as a library that end users would link against GCC, thereby avoiding the GPL (which only applies to distribution of the software, not how you use it). This little legal maneuver didn't work, however, so NeXT was forced to release the code.

Remember that an Objective-C implementation is in two parts: the compiler and the runtime library. NeXT was only required to release its compiler code, not its runtime library. As someone who has worked on an Objective-C compiler and two Objective-C runtime libraries, I can say with some certainty that NeXT didn't get the better end of this deal: For Objective-C dialects of that era, the runtime library is much more complex than the compiler.

Rather than admit that it had a worthless bit of code, the GNU Project wrote its own Objective-C runtime—and this is where things really started getting interesting. The GNU runtime wasn't quite a drop-in replacement for the NeXT runtime, so GNU needed to modify the compiler to support the new runtime. The modification involved a lot of #ifdef statements in the Objective-C support file. Of course, NeXT had no interest in supporting the GNU runtime, and therefore didn't bother to import these changes.

Periodically, NeXT would release a new version of its fork of GCC, and the mainline developers would try to backport their changes to the main branch. When Apple took over NeXT, the Apple developers continued to work on GCC, adding improvements such as better SIMD support to take advantage of the AltiVec units on the PowerPC chips that Apple was shipping. The developers also kept adding features to Objective-C. Because the Apple branch only had to support a single runtime library, there was no clear abstraction between the runtime-specific and runtime-agnostic bits, and so the GNU branch quickly fell behind.

The story doesn't quite end there, however. More recently, Apple wanted to integrate the compiler more closely with its IDE. One of the nice things about Visual Studio is that it uses the same parser and semantic analyzer for syntax highlighting and error reporting as it does for code generation, allowing for much better feedback than you get from editors that completely separate the two. Unfortunately for Apple, the GPL required either making XCode open source or rewriting GCC. Apple opted for the latter choice.

Fortunately, Apple didn't have to start from scratch, but instead was able to hire the lead developer of the LLVM Compiler Infrastructure Project, a BSD-licensed compiler infrastructure, and set him to work. The result was the creation of a new project, clang, to produce a new front end for LLVM that supported C, Objective-C, and C++. This front end currently supports the GNU runtime and the two Apple runtimes, and supports several features—such as fast enumeration and partial support for declared properties—that GCC doesn't, even when using the GNU runtime.

clang isn't the only Objective-C front end for LLVM, though; there's also one based on GCC. Unfortunately for people using non-Apple platforms, it's based on Apple's branch of GCC, and therefore only supports Objective-C on Darwin. This front end is covered by the GPL, whereas the one that has better support for the GNU runtime is covered by a BSD-style license.

What do we learn from this story?

First, we learn that you don't necessarily get good results from forcing people to do things. The NeXT Objective-C code was contributed to GCC reluctantly, and was never well maintained. The Apple code contributed to clang, in contrast, was written with a clean abstraction layer and allows new runtime libraries to be supported easily. This wasn't required by Apple, which started the project and therefore could do anything with it as desired. Because Apple willingly engaged the community, however, the end result is better for everyone.

The second thing to remember is that sometimes having someone else's code isn't actually a good thing. The Objective-C code in GCC is an unreadable, horrible mess. Objective-C is a small language, and the GCC team could probably have put together its own front end in a couple of weeks at most. If the team had done this, they probably would have designed it to support multiple runtime libraries from the start, and ended up with something a lot more maintainable at the end.

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information

To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.


Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.


If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information

Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.


This site is not directed to children under the age of 13.


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information

If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information

Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents

California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure

Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact

Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice

We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020