This is a port of SMSPlus, a Sega Master System emulator, to the 8bk-console, specifically of SMSPlus, version 1.3, by Charles MacDonald. SMSPlus itself (both the original as well as this port) is licensed under the GPLv2, as detailed in the 'license.txt' file. The Z80 emulator core Z80 normally uses has been replaced by the one from the EightyOne Z81 emulator (which itself is borrowed from Fuse, the Free Unix Spectrum Emulator) because the original version of the emulator core had an incompatible license; the EightyOne core is GPL licensed.