Just checked the make.bitsy.org website, and couldn't access it on chrome. Tried again on Microsoft Edge, and an ad redirecting site showed up, also saying that "this domain has just been registered". 

Does anyone know what happened, or why this is happening?

This is also happening to me (on firefox and chrome). make.bitsy.org/docs is also giving nothing. It looks like accessing the tool through the itch.io page still seems to work? (https://ledoux.itch.io/bitsy) Not sure what's going on though.

I’ll look into it!

It should be back online - give it a try now! Thanks letting me know :)