Heya,
As per their licensing page and FAQ:
"If you want to make money from your game, you need to buy a Commercial License for $99.99 .
If you want to export to Console you need the Enterprise subscription.
Other than that, everything else is free and unlimited!"
So as long as you're not making money in any way you'd be fine. I assume this also falls under taking donations for a game, so you'd have to be careful about that. You can also see that exporting to web or desktop is on the free tier alongside their GX thing. So you'd be safe on that front!