some modules needed for x11-wm/i3 test phases

> The implication I read here is that the absence of such an "or later" phrase implies "only".

yes. The license text reads pretty clear to me
> you have the option of following the terms and conditions either of that version or of any later version

That doesn't just mean the 'user', but anyone who redistributes it (me).
In addition... any form of ```or later``` is dangerous in my opinion, since there is no guarantee that GPL-4 will even be copyleft. From a legal point of view, no one should use that phrase, because it effectively means you trust non-existing licenses.

In that sense, the picked license is correct. But I have no problem with removing it.