"You may want to contact the Free Software Foundation to inquire what resources they have to offer to help open source programmers negotiate with their employers"

I emailed Richard Stallman of FSF about this and finally received his response:

"He should quit his job and find another. That will teach the employer a good lesson."

-- O thievish Night, Why should'st thou, but for some felonious end, In thy dark lantern thus close up the stars? --Milton