Clarify if GPLv2+ or GPLv2 only

[siraben]

Could you clarify if this is licensed under GPLv2+ or GPLv2 only? For more info, see this website.

[siraben]

Summary:

The Free Software Foundation urged developers to choose or any later version, since that meant users would be free to use that program under GNU GPL version 1, or under version 2 (once there was a version 2), or under version 3 (once there was a version 3). And they will be free to use it under version 4, if we ever have to make a version 4.

Two different copyleft licenses are almost inevitably incompatible in the absence of some explicit compatibility mechanism. That is because each one necessarily requires modified versions of a program to be released under that very same license. As a consequence, code released under GPL version 2 only can't be merged with code released under GPL version 3 only.