There's a lot of debate surrounding the GPL3 what it means for linux to switch to it. They're both fairly short documents but some interpretation of the consequences is required. So I'll attempt to summarize what it means to move to GPL3.

The GPL2 can be accessed by typing "man gpl" on any linux system (with man installed) and the current GPL3 draft can be found at "http://gplv3.fsf.org/draft". I should mention that I AM NOT A LAWYER. So I'll try to reference whenever possible.

* If anyone notices an innacuracy please post a comment.
* If they disagree with the GPL3, head on over and change it. They appreciate all input.

Linking Between GPL Versions

Practically, there is nothing preventing someone from mixing GPL2 and GPL3 licensed applications in their Distribution or libraries in their programs. Well, not usually. Almost every program in existence today that operates under the GPL2 will also operate under the GPL3.

But not unless they change the license. This is the tricky bit. the program itself may be fully compatible but every application has two different ways of permitting the license it can be used under. At this point they eiter say "GPL2" or "GPL2 or later". It's only a small change but every program has to permit the GPL3 license to be used before they can be used together.

Mostly the changes to the GPL focus on two core issues, DRM and patents. Broadly speaking, the new GPL forbids someone from writing a program that takes control of the computer away from the users and it prevents the companies who use it from defensively or offensively utilizing patents. This insures that one company which depends on GPL'd code can not sue another GPL using company, especially if they both use the same code but only one owns the patent on it.

DRM

Section 3, which used to be called "Digital Rights Management", now called "No Denying User's Rights through technical Measures", asserts that the license in no way allows someone to forbid the use of GPLd software, especially by invoking the GPL itself. It also asserts that "conveying a covered work" grants that person the full use of said work INCLUDING THE RIGHT TO CIRCUMVENT TECHNICAL PROTECTION MEASURES. So, if you give someone your software, you legally give them the right to break into it. This is a thorny issue but allowing the GPL to be used to repress people's free use of their computers didn't stick well with the editors.

It used to have a provision against spyware too. According to the "markup rationale" document. Surprisingly, people apparently disagreed. Enough to make you paranoid that the companies might be editing the document themselves.

Patents

According to section 11. The GPL guarantees that any distributed source is free of any patent trouble. Specifically, companies who attempt to enforce any patents they may posess in order to restrict any other GPL software user will lose the right to use their own code. The GPL3 guarantees the downstream rights of the users, which means that even if the company who sells your software loses the right to use it, you do not. However this is only so long as you adhere to the GPL yourselves.

Do we Need the GPL

This question cropped up at the ONLamp interview. (1) The best way to answer it is by mentioning that BSD is free software yet it's probably a safe statement to say that among companies who modify code for their own in-house use and who use linux as well as BSD. Most constributions go back to the GPL. The ONLamp interview mentions a similar example of Apache derivatives being used without any contribution to the Apache project. That's ok, however if such modified versions are sold, under the GPL they would have to be accompanied by the source and full GPL rights. Giving the receiver the capacity to change it themselves and therefore freedom from being at the mery of another company as well as the capacity to audit the contents of their software should they wish to do so.

Conclusion

Expect some teething troubles but it should help stop companies abusing each other with the GPL as a weapon. Didn't sony's root kit include GPL code? Would this stop them in future? Well at least we'll have tried.

Switching to the GPL3 only requires a small modification to the licences of the libraries involved. The changes themselves will be minute, but it does require everyone to work together and could cause problems for older programs unless someone takes over to change their licences.

References

(1) On Lamp
(2) GPL v3 Current
(3) Changes and rationales