The FAQ is just the FSF's wishful thinking, and not a legal document.
If your program can fork and exec another GPL-ed program, and exchange complex data structures with it, that is neither here nor there.
All that matters is whether or not you are redistributing the program, and if so, whether that is in accordance with its license, which restricts the manners of redistribution.
If you are not shipping that program, but your own GPL-incompatible program needs it (your program cannot be used unless the user has an installation of the GPLed program) then you're likely in infringing waters, because it could be seen as redistribution anyway. Though it you aren't physically redistributing the GPLed program on the same medium, redistribution of that GPLed program, carried out by someone somehow, has to take place for your program to work. It's as if you are redistributing it "by proxy". If the user doesn't have that program, you have to instruct the user on how to obtain it, thereby turning that user into an agent of redistribution, acting on your behalf.
But if you ship another program which is drop-in compatible with that the GPLed one, which allows your main program to run, then in all likelihood the GPL doesn't have a leg to stand on against you.
If you don't redistribute a GPLed program, in any manner, whether directly or "by proxy", you cannot be infringing on its license.
A GPLed program being combined with yours by the user, in their installation, has nothing to do with you, if that combining isn't a condition of your program being able to usefully execute. That is not redistribution but use, which the GPL does not restrict.
If your program can fork and exec another GPL-ed program, and exchange complex data structures with it, that is neither here nor there.
All that matters is whether or not you are redistributing the program, and if so, whether that is in accordance with its license, which restricts the manners of redistribution.
If you are not shipping that program, but your own GPL-incompatible program needs it (your program cannot be used unless the user has an installation of the GPLed program) then you're likely in infringing waters, because it could be seen as redistribution anyway. Though it you aren't physically redistributing the GPLed program on the same medium, redistribution of that GPLed program, carried out by someone somehow, has to take place for your program to work. It's as if you are redistributing it "by proxy". If the user doesn't have that program, you have to instruct the user on how to obtain it, thereby turning that user into an agent of redistribution, acting on your behalf.
But if you ship another program which is drop-in compatible with that the GPLed one, which allows your main program to run, then in all likelihood the GPL doesn't have a leg to stand on against you.
If you don't redistribute a GPLed program, in any manner, whether directly or "by proxy", you cannot be infringing on its license.
A GPLed program being combined with yours by the user, in their installation, has nothing to do with you, if that combining isn't a condition of your program being able to usefully execute. That is not redistribution but use, which the GPL does not restrict.