It's strange the article quotes so much from it, but doesn't link the BASIC source itself
These images: https://dialector.poptronics.fr/dialector_documents/ADisquet...
Plus this converter: https://github.com/KrisKennaway/ii-pix
...should get you closer. You'll still be missing a few files though, the full listing of the original disk contents (all the images, etc) is here: https://dialector.poptronics.fr/dialector_documents/ADisquet...
And yeah, as durakot pointed out it's Beagle Basic.
> At the risk of getting a bit esoteric, I want to spend a moment with the actual source code to Dialector [...]