Can the US Government release improvements to a GPL-covered program?
Yes. If the improvements are written by US government employees in the course of their employment, then the improvements are in the public domain. However, the improved version, as a whole, is still covered by the GNU GPL. There is no problem in this situation. If the US government uses contractors to do the job, then the improvements themselves can be GPL-covered.
Yes. If the improvements are written by US government employees, then the improvements are in the public domain. However, the improved version, as a whole, is still covered by the GNU GPL. There is no problem in this situation. If the US government uses contractors to do the job, then the improvements themselves can be GPL-covered.