The two paragraphs above what you quoted are:
"However, in many cases you can distribute the GPL-covered software alongside your proprietary system. To do this validly, you must make sure that the free and nonfree programs communicate at arms length, that they are not combined in a way that would make them effectively a single program."
"The difference between this and 'incorporating' the GPL-covered software is partly a matter of substance and partly form. The substantive part is this: if the two programs are combined so that they become effectively two parts of one program, then you can't treat them as two separate programs. So the GPL has to cover the whole thing."
Two programs communicating over a socket aren't incorporated. They're two programs.
I'm not super interested in fielding more thin gotchas based on out of context quotes. There's a big difference between a license that's difficult to understand and a license that somehow summons people from the ether who find endless ways to deliberately misunderstand it.
> Two programs communicating over a socket aren't incorporated. They're two programs.
Aren't they? So, if I want to use a GPL library, all I need to do is write a little wrapper program that does RPC over a socket, and boom, I can use a GPL library in my closed source program? Obviously not.
Yep. This is how MySQL/MariaDB work, for example.