Is it possible to put a web-based game on itch? I don't mean having itch host it in an iframe, but actually direct to the web-based client from my own domain. There's no feasible way I can have itch host it (the game is an mmorpg made with evennia, django, twisted, and on a server of it's own). 

Basically, can put this on itch somehow?

If your community uses some kind of dedicated tool to play the game (like KoLmafia for Kingdom of Loathing) you could probably upload that - or ask the developers to upload it, if it’s a community driven project.