There has been some recent interest and discussion about whether a contributor of open source code can take it back at some point. That is, can he take it out of a GPL license? The answer is NO. This “NO” is implicit in GPLv2 and explicit in GPLv3. In other words, a number of sections in the GPLv2 license terms make it highly unlikely that a court would honor a contributor’s effort to rescind his open source licensing of this code. The GPLv3 license directly addresses the issue and expressly prohibits such un-licensing, stating:
All rights granted under this License are granted for the term of copyright on the Program, and are irrevocable provided the stated conditions are met.
The reasons for this are fairly obvious. It’s called reliance. Once downstream coders have used the open source code, and yet others even further downstream have built on that, it’s out there and the original contributor cannot just pull the rug out from under those who have relied on this original licensing. For further discussion see this ZDNet article.