IIRC they found a way around the Sega licencing system for the Megadrive too
That was Accolade. Basically what Sega did was two things. First they put in a 256-byte phantom boot ROM which displayed the "produced by or under license from SEGA" message, delayed for a moment, then started up the external cartridge ROM. The second thing was a watchdog timer that would reset the system a moment later if a new hardware register wasn't written with the 32-bit ASCII code for "SEGA".
Accolade's "workaround" was to literally copy the first few dozen bytes of the cartridge startup code from a Sega game. Then Sega claimed a copyright violation on that code. First, it was dumb of Sega to think that they could win a copyright case for that small amount of code, and which was made necessary by the hardware. But second, it was dumb of Accolade to not simply rewrite it to use different instructions, because the necessary code wasn't that forced.
Also, (going by memory here, it's been a while since I looked at how this works), did you notice the part where the licensing message was put on the screen BEFORE ever accessing the cartridge data? Yeah, totally not Accolade's fault that it was already on the screen. Or I guess you could say "yep, that phantom ROM was produced by Sega, sure was!"