MESS (http://www.mess.org/) is a sister project of MAME. SDLMESS (http://rbelmont.mameworld.info/?page_id=163) is, obviously, an SDL port of MESS. instead of arcade machines, MESS emulates various classic computers. MESS support would be a great addition for GMAMEUI, especially since there are significantly less frontends for MESS, than for MAME. I believe there should be little problem with implementing this, MAME and MESS work in a similar fashion.