The GNU GPL was a way to infect all software and make it public. It did not work because courts did not accept it as defensible. But my company on the advice of several lawyers rid ourselves of all GNU GPL code. The language was a bit vague. But it could certainly be interpreted to mean that any code that was used in conjunction with GNU GPL code was for ever more also general public code.
I negotiated thousands of software contracts. I even negotiated some software contracts with Microsoft. Their lawyers and ours agreed on this point. And it matters a great deal. Not because Microsoft wants to own the world, or creates the best code. The reason they care is because all Microsoft contracts state that they have the right to sell or license their code. And you can’t make that point if its public domain code.
Another issue with public domain code is that it can have viruses. All code can. But if your programmers are borrowing anything they find on the web and using it in their code, who knows what back-doors are in the borrowed code.
I understand that IBM went early to Linux and GPL. And that Microsoft changed their stance. But they are still careful of code that is not homegrown.
Open source can certainly have bugs, but it’s pretty hard to hide a virus in it when anyone can read the code.