I think the FSF sorted that out, although I haven't seen their paperwork. It popped up a lot some years ago, and it seemed to have been solved.
I suppose in most countries, one cannot sign away personal copy rights. You are always the author. But one can easily give right to use the work because of author's economic rights (and one must obligatory specify the fields of exploration in such agreement).
In Germany, you cannot legally sign away copyright (i.e. signing away your copyright is either an empty action or may even void other agreements contained in a larger contract).