The GPL appears to be rather clearly a contract license when it governs the give and take inherent in shared open source development within a community. Your points regarding gratuitous licenses seem applicable where publishing has occurred but no further open source development has taken place -- and this seems largely irrelevant to concerns regarding an existing open source community.

I'm not sure why concern would be raised with respect to the original contract offer. It seems entirely irrelevant given that any participant has full rights under the contract terms.