See my comment below about that.

The developer who wants to combine with closed source can contact us and work out a special deal. It's only fair. They want to be compensated for spending their time, then so do we.

Yes, but then don't talk about "freedom to use"... if something else must be done before that usage.

It isn't freedom to use unconditionally. It's freedom to use if you do same as we did for you.