- The GPL Bargain
- Copyleft and Reciprocity
- Policy Objectives
- The Preamble to the GPL
- GPL as Template
- The GPL Applies to Programs
- Linking to GPL Software
- Copyright Law and Linking
- The LGPL Alternative
- GPL Grant of License
- Access to Source Code
- "At No Charge"
- Other Obligations in the GPL
- The GPL and Patents
- Accepting the GPL
GPL Grant of License
The first place in its terms and conditions that the GPL mentions its license grant is in the negative:
Activities other than copying, distribution and modification are not covered by this License; they are outside its scope. (GPL section 0.)
Thus are the first three exclusive rights of a copyright owner from 17 U.S.C. § 106 introduced. (Refer to the discussion of the exclusive rights of copyright owners in Chapter 2.) The license grant is stated in an affirmative way later in the GPL:
You may copy and distribute verbatim copies of the Program's source code as you receive it, in any medium, provided.... (GPL section 1.)
You may modify your copy or copies of the Program or any portion of it, thus forming a work based on the Program, and copy and distribute such modifications or work under the terms of Section 1 above, provided.... (GPL section 2.)
You may copy and distribute the Program (or a work based on it, under Section 2) in object code or executable form under the terms of Sections 1 and 2 above provided.... (GPL section 3.)
These, plus the source code grant discussed in the next section, are the required grants to comply with the Open Source Principles listed in Chapter 1.
You may have noted that the GPL does not grant all the rights under copyright; missing are licenses to perform the work or to display the work publicly. For most software, that's not important.
There are more interesting things than that missing from the GPL's license grant. The first and most important is a patent grant. The GPL does not expressly grant rights to make, use, sell or offer for sale, or import software that embodies the licensor's patents. This omission is important for a bare license like the GPL, because nothing in the law requires the licensor of copyrights to also license his patents. Bare patent licenses are not implied.
The GPL attempts to solve this problem by including the following condition:
If a patent license would not permit royalty-free redistribution of the Program by all those who receive copies directly or indirectly through you, then the only way you could satisfy both it and this License would be to refrain entirely from distribution of the Program. (GPL section 7.)
In other words, a licensor cannot distribute software under the GPL while simultaneously demanding royalties for his patents. His act of distributing the software implies a royalty-free license.
As to the scope of such an implied patent license, can we assume that it extends to the creation of derivative works since the GPL contemplates that licensees will create derivative works? That is possible, but there's nothing in the law of bare licenses that requires that result. Any company intending to create and distribute derivative works under the GPL ought to obtain separately the patent licenses it needs.
The second item that is missing is a statement of what other intellectual property rights, if any, are intentionally excluded from the license grant. For example, suppose a GPL-licensed program bears a trademark and that trademark is printed out by the program in some initial welcome message. Does a licensee under the GPL have the right to apply that trademark to his or her own derivative works? Must the licensee remove the trademark from executable versions of this derivative work? The GPL is silent on that point.
The GPL is also silent about the scope and duration of the licenses it does grant. One can assume that the license is worldwide, consistent with the open source definition. One can also assume that the license is perpetual, since there is no mechanism for terminating the license as long as the licensee complies with the terms of the license:
You may not copy, modify, sublicense, or distribute the Program except as expressly provided under this License. Any attempt otherwise to copy, modify, sublicense or distribute the Program is void, and will automatically terminate your rights under this License. However, parties who have received copies, or rights, from you under this License will not have their licenses terminated so long as such parties remain in full compliance. (GPL section 4.)
This GPL section 4, with its negative wording, is also the only place that references the right to sublicense. One might assume from the way GPL section 4 is worded that the right to sublicense was intended in sections 1 (right to copy), 2 (right to modify) and 3 (right to distribute) as well. However, section 6 implies that there are no sublicenses but instead a direct license from each up-stream contributor:
Each time you redistribute the Program (or any work based on the Program), the recipient automatically receives a license from the original licensor to copy, distribute or modify the Program subject to these terms and conditions.... (GPL section 6.)
As to sublicensing, then, the GPL is ambiguous. I refer you to the discussion in Chapter 5 of sublicensing in the MIT license. Sublicensing rights can be very important to open source distributors for dealing properly with the chain of title to contributions. In practice, most software projects ignore the issue completely and assume that, for GPL software, only the most recent license in the chain of title matters. They assume that GPL licensed software is sublicenseable, but the GPL isn't clear about that.