Actually, Netscape was not derived per se. It was a complete re-write by people from the Mosaic team who had left to start Netscape. Microsoft licensed Mosaic

Actually, Netscape was not derived per se. It was a complete re-write by people from the Mosaic team who had left to start Netscape. Microsoft licensed Mosaic from Spyglass, who held the rights by virtue of a deal with the University of Illinois.