If it's opensource under the usual OSS licenses, the former emplpyee can only demand something for further work/improvements, not for already existing code. An

If it's opensource under the usual OSS licenses, the former emplpyee can only demand something for further work/improvements, not for already existing code. And companies typically have no trouble critically relying on OSS projects they have no chance of forking/maintaining if something changes that they can't accept.