Reaper 2k2 who as of late has been very active in the Dreamcast scene has ported his first emulator using SDL, heres a little more from This Forum Topic

Well ive been working on so many thing they were geting me down and we all like space invaders dont we ?

so i ported this emu its a fully space invaders emu supports thoses romsets at the moment its keyboard only and has no sound yet it it will when SDL sound is fixed

Check the link above for more information.