There are real reasons to keep an eye on Apple and MS to make sure that they aren't abusing the Open Source community for marketing purposes. They are large companies that, should they see an advantage in doing so, they would not hesitate. This doesn't really help.
That being said...The "Open Source .Net" that they refer to in the article is actually a commerce platform from a third party that says it "takes advantage of open source Asp.net". Is that really so wrong? Asp.net has been open source for several years now. .Net core design meetings are available as streamed video if you want to join in and the license is MIT.
Also, articles that quote Stephen Vaughn-Nichols are like articles that quote FOX or ZeroHedge. I'm just automatically suspicious. Oddly, they quote him on this "open washing" but he doesn't seem to have problems with large companies publicizing the use of OpenStack or partnering with Canonical or any number of PR style things.