Very cool! Was it difficult to get Bitrig approved on the App Store? If I had to guess just based on the idea, it seems like the sort of thing Apple would take issue with.

Heh... it definitely wasn't an overnight approval. However, Apple has relaxed the guidelines for developer tools compared to the early days of the App Store. If you look today there are Python IDEs, Jupyter Notebooks, and various other apps that execute user generated code. The key guideline to be mindful of is 2.5.2.