This is a bit like Fay, is it not? I'm not skilled enough in either languages to cite the differences, though pureScript does not seem like it's strictly adhering to haskell syntax.
Basically, I wrote this partly just for fun, but also because each of the current options (Fay, Elm, Roy, TypeScript, etc.) all had some small feature I wanted to change. The biggest factor for me was the generation of compact, readable, debuggable Javascript.