itch.io

I'm almost positive it's just a false positive. Your antivirus is being overzealous. Formamorph itself, in the back end, is just an HTML (a web page) that is opened with an embedded web browser (Chromium based)

You can download them into a JSON file, which is just a text file you can then send/share with your PC/phone.  You can do so by opening the world in edit mode and clicking on Download. 

Nope, as long as it's OpenAI compatible it *should* work.   At least, from my testing that's been the case.