There's a github repo trying to rewrite it for the web: https://github.com/jackinloadup/lunatic-fringe

There's also this, which I vaguely remember working for me years ago, but can't vouch for now: http://www.sealiesoftware.com/fringe/

I have incredibly fond memories of playing Lunatic Fringe, despite being very bad at it, and despite catching a ridiculously bad case of strep throat one year shortly after discovering it, and having some bad, vaguely-related fever dreams about.