Hi there !

Provided that other rules are respected (such as 4 colors only), can we enter the jam with a Pico-8 game, that is restricted by 128 x 128 pixels ? With the Gameboy aspect ratio constraint (1.111 x 1), could I use a 128 x 115 pixels resolution ?

Go for it. As long as the colors are limited to 4 on the screen at any given time then pico8 is fine. You can use the whole 128x128 if you wanted to. We try not to be overly strict to ensure the jam is accessible to as many people as possible; so as long as you can get close, you're golden.

yes, resolutions below 160 x 144 are allowed if it’s an engine-restriction like Pico-8.

it is mentioned in the FAQ in past jams (which hasn’t been added to this year’s page yet). i don’t expect the rules to change much this year. here is last year’s jam page for reference: https://itch.io/jam/gbjam-13