I knew about the soft copyleft (the source code requirements) but didn't know there was the requirement to have libs be replaceable. Now I want to know how useful that would be in reverse engineering closed systems (particularly nintendos, since I've always had an interest in the homebrew scene there)

iirc, the video player application VLC used to come without any mpeg support, and you had to go through a process to download ffmpeg separately ...not sure how easy it made it to replace individual libs, but I'm also not sure the license requires you to make it easy.