You're Either with Us or Against Us
The FSF makes two sets of Free Software licensesone that's GPL-compatible, and one that's GPL-incompatible. This is an interesting spin, because most of the "GPL-incompatible" licenses are per-file, allowing you to combine them with code under any other license. The GPL places additional restrictions on the code, and therefore is incompatible. You can combine APSL, MPL, CDDL, Apache, and BSD-licensed code in the same project easily, but you can only combine one of these with GPLv2 code.
Even the Free Software Foundation can't manage to get it right. Version 3 of the LGPL, for example, is incompatible with version 2 of the GPL. This has caused a problem recently for a few GNU library projects that wanted to move to LGPLv3 but were used by other projects that were GPLv2-only.
The official stance is that projects shouldn't be v2-only, they should always be v2-or-later. I'll let you try to persuade Linux to switch. Oh, and good luck with PDF readers, too; the only open source PDF readers at the moment are based on xpdf, which is GPLv2-only. The FSF is frantically trying to write a new PDF library to get around this limitation, and licensing it as GPLv3-or-later.
This attitude is understandable. Richard Stallman believes that writing proprietary software is antisocial. Unfortunately, this mentality leads to lost opportunities. The GPL doesn't give you the choice of writing some proprietary software and contributing it to Free Software. If you want to use some GPL'd code, you have to GPL your entire project (which is sometimes impossible due to third-party requirements).
This is where the FSF and I have a fundamental philosophical disagreement. I believe that the community benefits when the amount of Free Software increases. The FSF believes that the community is harmed when the amount of proprietary software increases, and that making it easier to write a proprietary application is a bad thing, even when the side-effect is that the developers improve some Free Software.