Sure, here's the repository: https://github.com/JohnEarnest/ok

I don't have a rigorous approach for testing compatibility at present; My starting point was the K2 manual, and I've tried to get as many examples from that working as possible. I have been learning the language as I go, so often I don't realize functionality is missing until I stumble across an existing K program that doesn't work properly.

I'm targeting K5, which is unreleased, so there's a great deal of speculation. I think I have a decent subset of the functionality working now, but most of the time when I write new programs using it I still shake out bugs and unhandled edge cases.