That's extremely difficult to enforce for such a small company, and PICO-8 Games (and fantasy console games in general) are rarely profitable, so it wouldn't be enough to make a living.
If you're looking for an open source/free tool I reccomend TIC-80 (which has a pro version for 10$, though you can go to the github repo and compile the pro version for free, and they even encourage it) or PixelVision8 (although PV8 isn't very simillar to PICO8 or TIC-80 from what i've heard.)
The Unity Business model just doesn't work for this type of tool.