I have to disagree. There are two use cases, reading and changing the source. When Microsoft only allows very limited contributions to the source it either beco

I have to disagree. There are two use cases, reading and changing the source. When Microsoft only allows very limited contributions to the source it either becomes effectively read-only or it will get forked. If it gets forked they will sooner or later face the decision to either compromise on their design decisions in order to maintain compatibility with forks or they start going down the fragmentation road leading to compatibility issues. Only reading the source is a different story. It should actually be a exceptional use case, for example for debugging, but besides that you should of course usually not worry about implementation details or even take dependencies on them. And Microsoft's documentation of the public surface is pretty good and therefore there is rarely a need to look at the source to understand the functionality. Finally at least for research purpose it has been possible for a long time to obtain a copy of the source, not sure if this is possible or how hard it would be for non-research purposes.