Imagine that instead of developing an app in a popular programming language, someone implements an idiosyncratic domain specific language suitable for the kind of app they need to build, and then builds the app using that. The result would work and maybe even let them be very productive churning out more features of the kind that were envisioned when the DSL was developed. If they need to extend or fix the DSL, as the original author, they can. Someone else will need to learn the DSL before they can do any work on the app.

wolf550e summed it up pretty much perfectly.

There was a great deal of thought put into it and he could extend and modify the output really quickly.

The complexity of the system basically made it so that what would otherwise have been a simple task achievable by a graduate required a deep understanding to carry out.