I started writing a series of articles about Pragmatic Category Theory in OCaml, and there’s a repository with examples:
If you’re interested in a complete project, I made CCL: Categorical Configuration Language which leverages multiple Category Theory concepts:
I’m currently working on a GitHub TUI project in OCaml but the usage of CT concepts is not that crazy there. For now, I only use Semigroup and Monoids (which some people don’t even consider part of CT but just Abstract Algebra).