I think there's a good chance for any company paying a developer to write something that a good chunk of their software includes free and open source stuff,especially if you include cloud resources. Even Azure is pretty heavy on Linux, and other Microsoft technologies have gone free (if not also open source) in an effort to retain mindshare. Java is free, C# is free, eclipse is free, many, many libraries and tools are free.

At this point its probably easier to list the non-free things in the average stack or development pipeline than the free things.