> The problem is that documentation comments are embedded within the source code, potentially in _any_ file. You either have to dual license the entire project under the GFDL, or make a silly clause like «any comment anywhere in the source code is also licensed under the GFDL», something that I doubt you're allowed to do.
It works if you apply the policy before you start creating documentation comments, which would make some sense. Then you just reject patches that don't comply.
Or if you mark "approved" documentation comments in some way.