Here are just a few examples I found of evidence in just a few minutes of searching:
https://slate.com/technology/2005/11/the-open-source-movemen...
https://www.wired.com/2014/07/tech-time-warp-ms-matrix/
https://www.latimes.com/archives/la-xpm-2002-dec-26-fi-micro...
The legal questions were always overblown. The concern Ballmer was raising was that if you incorporate a bit of GPL software into your own, then it could "infect" the rest of your code and force you to release more. But that's ridiculous because nobody is forcing you to incorporate GPL software into your own. There was no serious legal concern about simply using Linux - Microsoft was just trying to scare people.
Is Microsoft a different company today? Yes, in many ways. They're much better about open-source software, for sure.
I still think they're anticompetitive in many ways. Their marketing team still prefers to try to spread lies about their competition (e.g. Chrome) rather than promote their own product on its own merits.