The CCA isn't a software license issued to end users, like the GPL; it's an agreement contributors sign giving Canonical rights to their code. It looks like a l

The CCA isn't a software license issued to end users, like the GPL; it's an agreement contributors sign giving Canonical rights to their code. It looks like a less-restrictive alternative to copyright assignment, which the FSF requires for contributions. What is GPL incompatible about it? Note that it includes "a promise back to the contributor to release their contribution under the license in place when they made the contribution" (http://www.canonical.com/contributors/faq http://www.canonical.com/contributors/faq).