There are plenty of companies that may not use the full BSD stack but pull bits and pieces of code as needed. Microsoft is known to have built off BSD networking code for Windows.
>Microsoft is known to have built off BSD networking code for Windows.
30+ years ago, when everyone was basing their TCP stacks on the BSD implementation. That was one of the reasons that the infamous 64k+ "ping of death" affected more than just Windows in 1998.
The stack was re-written for Vista/Longhorn more than 20 years ago.
My point being that the GP question was about FreeBSD's success today and the Windows TCP stack is not a good candidate to illustrate that.
You can infer others if you look at the historical sponsor pages: https://freebsdfoundation.org/our-donors/donors/
There are plenty of companies that may not use the full BSD stack but pull bits and pieces of code as needed. Microsoft is known to have built off BSD networking code for Windows.