The GH issues hint this is not maintained? The site itself seems to be working, though.

Although since recently I have been using https://github.com/technoboy10/crossorigin.me without any downtimes or ssl issues. (I am not related to any of the two projects in any way, though.)

That's what i love about open source. You have a problem, solve it and others can benefit from it and even extend your solution.

Great work