Though in the case of .NET core they'd have to extinguish their own ecosystem that was closed source, then they open sourced it and they partially opened the de

Though in the case of .NET core they'd have to extinguish their own ecosystem that was closed source, then they open sourced it and they partially opened the development process that was completely internal. For developers in the .NET ecosystem the OSS-ification is a net win (pardon the pun). If you are a Newcomer to .NET, you still should expect that Microsoft has some control over the ecosystem, just as the rest of the community also has certain rights and powers (through forking and patching) if it comes to that. Microsoft also controls part of the Node ecosystem (npm) and Typescript. Google controls Android and Angular. There are always tradeoffs, it's more important to be aware than to avoid all of them.