This seems to be intended as an interesting experiment (in the same genre as things like quines). There are obviously more production-ready ways to compile code for multiple runtimes.
Haxe is not just an experiment. It is a mature language and ecosystem used in production. You will find it powering many games for example.
I used it a long long time ago on one of my first freelance gigs (with a PHP target). It was already quite solid and saved me the need to use a PHP framework.
I also remember using it as a typed javascript pre-compiler, at a time where FB Flow and MS Typescript were still fighting over developer mindshare. I would probably still use it if TS didn't take over the ecosystem entirely.
"This" = Polycompiler (the OP project), not Haxe. Polycompiler appears to be intended as a toy/experiment, so it doesn't really make sense to compare it to Haxe.
