"Oh god, do we need another language that compiles to javascript?!"
—Everyone, probably
—Everyone, probably
I think this looks like a great project, we can never have too many programming languages to play around with.
Wait until we start having legacy code in all those languages.
>we use 30 different compile-to-js languages used in our projects(that are no longer being developed) and you have to maintain it.
(Like a company I know which picked VB 6 and still hasn't fully migrated away from it. The same company picked Microsoft's AJAX demo as a basis for a JS framework and is still developing that even though MS long since abandoned it. Would it be better to use jQuery, Angular, Ember, React, Riot, etc? Well, those are too new and untested. Very conservative leadership.)
Anyway CoffeeScript and JavaScript work well together and you might want your code to be in CoffeeScript but you have to use a library, say Ember (also a real project at a different company) which means certain improvements, bug fixes, etc. to Ember are done in JS. There's two. I'm sure you could easily end up with multiple libraries written in multiple compile-to-JS languages.
Long-term code maintainability is a bit of a hard problem. You probably need to be constantly refactoring, rewriting, and re-inventing so you don't have too much old code in play anyway. Maybe. What do I know?
Competition is good, competition is creativity.
More like "write once, run in the browser". I don't think most compile-to-js languages care too much about "anywhere", they are just trying to get nicer alternatives in what is basically a platform (the browser) closed to anything except JS.