[Denvercoder9]

> Unless I'm missing something, the "or any later" clause means that a new GPL would cause further software releases to be dual licensed as GPL v2/3 and 4.

It also causes past releases to be immediately and retroactively available under the GPL v4 (in addition to the GPL v2/v3 it was already available under). As such the FSF has the power to make a large amount of software available under a new license.

> I can only imagine that causing problems if they say released a non copyleft v4, and it's hard to see that surviving a legal challenge.

A hypothetical GPLv4 has to be similar in spirit to the previous GPL licenses, but the devil's in the details -- just look at the prolonged debates about GPLv3. Depending on the exact details it might not be acceptable to parts of the free software community.

[boomboomsubban]

> hypothetical GPLv4 has to be similar in spirit to the previous GPL licenses,

This doesn't cause an issue though, the software is still licensed under v3. A more restrictive v4 can be ignored, an issue would only arrise from a less restrictive v4.