It isn’t moral relativism. It’s just economic sense. In both cases.
There is no moral requirement to be open source.
Being closed is not fraud, coercion, theft, dishonest, anti-competitive, …
(On the other hand, being open, in situations where closed would be more profitable, is taking the moral high ground.
Open provides better value for the customer, user, and community.)
Aside from moralizing, the economic puzzle is: How to align the economic incentives of businesses with the real long term community value of openness. While also providing greater resources to successful innovators to incentivize and compound there best efforts.
(Note that copyright has been the solution to this problem for cultural artifacts. And patents try to do this for tech, but with more problems and much less success.)