It’s a touchy subject because of the nature of the engine and working with it (and it’s source) but source distribution of /module code should be an option, not a requirement. Intellectual property and privacy concerns are key in this matter. Epic choosing to distribute source to it’s customers is their own decision (and omg thank you so much for that decision!!!) but our own business models should not have to reflect theirs. To be honest, I don’t personally even like the idea of external language bindings being required to be open-source because it pretty much negates the possibility of someone making a viable business venture from providing a proprietary binding to UE4, however I can understand this limitation because there would be nothing stopping someone from wrapping the entire engine and marketing it as their own with UE4 binaries linked against it.
A is a piece of software and should be treated like any other product developed with the engine (games, assets, etc) and source distribution should be up to the provider, otherwise, how else are we expected to protect our intellectual property if we desire to do so?
For those worried about developers not keeping their plugins up to date or waiting for them to provide an update: That’s the nature of the game. Choose your vendors wisely. If source distro is forced, there will be a lot of vendors opting out of selling on the market place and that doesn’t only hurt them, it hurts the community because the marketplace is the official spot to find things and some of the best will be closed source. That’s just the way it is.