It's actually a bit worse than open core, in that the closed source version of the program works with versions of Python that have not been end-of-lifed [1] but the open source version of the program does not [2]. Because of that I'm not comfortable calling this open-anything.

This is a closed-source program that used to have a open-source version, which is now abandonware.

[1] https://devguide.python.org/devcycle/#end-of-life-branches

[2] https://build-system.fman.io/manual/#requirements