Hello!
That is correct, I am developing it with Raylib. I appreciate your offer for assistance!
While I don't need help on anything directly currently at the moment, you can feel free to assist by means of opening pull requests for features to implement. You can ask here or on my Discord server to get some guidance on things to work on. For example, there's features that haven't been implemented that are visible in the plan project for MasterPlan itself, which is available as the master.plan file on the Github repo itself, or some publicly facing To-do lists available in this thread here.