I recently interviewed for one of these open source dev positions (Proton). From what I could gather from my conversations with the hiring manager, its somewhere between 120K to 160K for C Devs.
Yes, that's one possible solution to the issue of out-of-print works. Compulsory licensing or royalty payments for these works could provide a way for them to be republished and made available to the public again. This would create value by ensuring that these works remain accessible, and by providing a financial incentive for publishers to republish them.