purescript

I'm curious why this isn't a backend for the existing PureScript compiler, since the front-end seems to be copy-paste identical?

PureScript has a lenient FFI so you can choose to use 99% pure functions if you like (at your own risk).

Yes it does.

This seems like it could be useful, but I don't seem to be able to create a discussion which is visible to everyone, yet only editable my members of my team, which is my main use case (for discussing project direction and such). "Public" seems to mean "visible to everyone in the organization".

Category theory matters to programming because, among other things, it teaches us how to abstract over programming languages. What better definition of abstract programs than "things with types which compose"?

Now consider categories with various types of constructions (products, limits, exponentials, etc.) and you'll notice they correspond to requiring certain features in your language.