Thanks for the interest but a web version is unlikely. This was written in Java and I've since transitioned my game engine to C++. In the future, an improved Windows version or sequel is possible.
When it was released, Demon's Hymn 2 originally supported MacOS. One of Apple's updates broke it and it shows a black screen, from what I heard from other Mac users. I'm unable to verify that personally.
If a new Windows version is made in the future, it may be runnable on Mac using Wine but I can't guarantee it'll work. I'm focusing future development of my games on Windows because it's my primary OS and because on Steam, 96% of users are using some version of Windows.
I'll keep it in mind that there's interest in a web version though- It's not impossible but I have to focus on other projects for the time being.