Easy to avoid depending on the area; I'd urge you not to be discouraged by the presence of commercial libraries. They aren't as vital as it may seem from the outside. I've been a full-time C# developer since the first open beta and I have only one (1) instance where I used a commercial library. That was 2002 and if we were doing it today, we wouldn't have needed that commercial library. I have never used a commercial C# library other than that one time. We have a tremendous supply of open source libraries in NuGet, just like every other language, and much more functionality built into the standard library than most languages have. We just also have commercial UI libraries and such. That commercial library we used was a docking/tabbing UI library; you can get that from open source packages now (and my later projects do).