If that happens then I'm packing up and heading for the hills, this world is done for.
https://www.gnu.org/licenses/gpl-faq.en.html#DoesTheGPLAllow...
I'd argue otherwise[1].
Also, as of ~2 years ago, CentOS is just another Red Hat supported project.
Some people probably said that about the .NET framework. Now almost all of it (the new stuff anyway, and minus Visual Studio) is fully open source.
If someone is licensing something under GNU GPL, they are also giving away their intellectual property/patent rights (or what ever they call that) to any software developed in GPL, which Microsoft is never ever going to do.
MIT/X11 license is not giving other developers and users such a patent protection from its original developers.
B) Modern MS-RSL "reference source license" is now OSS compliant. The remaining difference between .NET Full Framework's Reference Source and what's happening with .NET Core is .NET Core has moved development to the open and Github as primary development platform. .NET Core is the future and .NET Full is "stable".
C) One example: http://referencesource.microsoft.com/#PresentationFramework/...
There's nothing stopping you from using the Reference Source today to build your own WPF fork (or, let's face it, you probably mean SWF). You can even start with Mono's existing mostly-there cross-platform SWF or Moonlight codebases and save a bit of time.
You know why you don't hear about lots of people doing that? I'm fairly certain it is because no one is building cross-platform GUIs in anything but HTML(5) these days.
On the other hand, at my current job I've been in charge of some search tech that's Windows only and being the lone Windows user has been a bit painful. We liked the results it gave us but recently developed our own algorithms on top of ElasticSearch so we didn't have to deal with Windows anymore. The Dev work to switch was more than the cost saved on the license for the old software, so this wasn't a case of open source saving is money on the solution implementation. We really just didn't want to focus on Windows Dev ops. I think this is the concern the SQL Server team had and why they're supporting Linux, especially in Microsoft's increasingly Azure focused world.
My income depends on SS but it saddens me when I think of how much is spent on it by applications which could so easily run on something that is free.