It's perfectly legal to redistribute binaries because the Quake II source code is GPLv2. It would even be legal to redistribute the shareware PAK files. (but don't bother) It just wouldn't be legal to redistribute the commercial PAK files.
I'd appreciate your sharing, but ultimately, I'd like to get Quake II added to the RetroPie setup script. That would make it easy for people running RetroPie to set up and start playing Quake II.