I thought the point of CLA's in general is to stop contributors from revoking their license, or claiming the entire program is a collaborative work and that the

I thought the point of CLA's in general is to stop contributors from revoking their license, or claiming the entire program is a collaborative work and that they have joint copyright over all of it. I don't think either has ever happened in open source, but I believe is possible, at least in the US.