That goes beyond what most people consider the GPL to cover. There are other licenses with stronger copylefts specifically to cover that last case -- notably, the AGPL.
I suspect trying to make the case that GPL's viral copyleft isn't limited to strictly linking but potentially any interaction with it would probably have a chilling effect on the use of GPL code, and this reinterpretation would only reinforce some people's prejudice against the GPL, a la Ballmer's "Linux is cancer" line.
Maybe it's the pragmatism in me, but I think it would have a net negative effect long term, unless it managed to flip all of the tables and convince everyone to use all GPL code, instead of making people reject copyleft wholesale.
But that's not what I said. I said programs that do not work without some other program, is, in my opinion, a derivative work. I just don't see how the calling mechanism even plays into that judgement.
I do agree that there are other licenses such as the AGPL that try to cover these cases.
And arguably the online thing is a whole different ball of wax, because you can talk about software using a service, etc. It really is tricky in that case.
But I don't see the reason to distinguish between calling a function via the C stdcall mechanism, vs. "popen" and capturing stdout. It's exactly the same, logically, the only difference are details that imho should not matter for the legal case.
Right now, if I release a GPL library, what stops someone from coming along and writing a CLI program that just wraps every function with some textual interface, and including that with their closed-source program? The GPL becomes pretty toothless if it's bypassed so easily.
I suspect trying to make the case that GPL's viral copyleft isn't limited to strictly linking but potentially any interaction with it would probably have a chilling effect on the use of GPL code, and this reinterpretation would only reinforce some people's prejudice against the GPL, a la Ballmer's "Linux is cancer" line.
Maybe it's the pragmatism in me, but I think it would have a net negative effect long term, unless it managed to flip all of the tables and convince everyone to use all GPL code, instead of making people reject copyleft wholesale.