Version 3 of the GNU General Public License will soon on the horizon. Richard Stallman the father of GPL, GNU project and FOSS activist / hacker recently explained why you should upgrade from GPL 2 to GPL3:
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First of all, it is important to note that upgrading is a choice. GPL version 2 will remain a valid license, and no disaster will happen if some programs remain under GPLv2 while others advance to GPLv3. These two licenses are incompatible, but that isn't a serious problem.
When we say that GPLv2 and GPLv3 are incompatible, it means there is no legal way to combine code under GPLv2 with code under GPLv3 in a single program. This is because both GPLv2 and GPLv3 are copyleft licenses: each of them says, “If you include code under this license in a larger program, the larger program must be under this license too.” There is no way to make them compatible. We could add a GPLv2-compatibility clause to GPLv3, but it wouldn't do the job, because GPLv2 would need a similar clause.