"Open source" and "commercial" are not antonyms, but people working on proprietary software think they are.
The sort of access to source code that is being expected here is really no more than the sort of access that you can get to Windows code. It really is not an unreasonable expectation.
I suppose that you, however, do not, which makes what I was trying to say irrelevant.
I do think there is a commercial side to this, too, however. This is a kind of a hook to catch future customers of the commercial package.