Sorry for taking this long to reply. I was checking with the other hosts and with the community (over at the discord) and everyone agrees to open an exception for PICO-8 games! The engine is still very retro looking and you have no option to increase the resolution. The important part is that the game feel like it's a GB game
as far as rules go, the GB jam is great is because it only has 2 rules!
If we allow 128x128, isn't it drifting a bit too far from the GB theme?
GBJam has always been pretty casual. It's not as much a competition, but a gathering of people who want to try making a game based on the GB
That's why I asked the community for their input on this question and the response was overwhelmingly positive. But this is still a specific exception. If someone makes their game 64x64 (like LOWREZ Jam) or they use 5 colors or pure mouse controls, we will remove that entry
There are other GB jams out there (there were like 3 just between this month and July!) some more strict than others, I'm pretty sure there was even one where you needed to use ASM programming, so there's something for everyone