Yeah, sorry. I think that was a poor choice of words on my part.

For instance, if you have a website that uses AGPL code to produce an HTML page and non-AGPL code to provide a PDF from that HTML page, the two packages would indeed touch, but there would be no obligation to release the non-AGPL code, just the AGPL code.

Interesting, in your example, if your application calls the AGPL code that is used to generate the HTML wouldn't your application also have to be released under the AGPL? Or do you only have to make available the AGPL "HTML generation library" and the changes you have made to it (if any)?

I thought that it had already been established that if you use a library under the GPL any code that uses/calls that library must be released under the GPL. The only reason companies can use GPL code server side is because it is not run on the user's machine (technically not "releasing it"), which was the basis for the creation of the AGPL, to "fix" this "loophole".

edit:

Thanks skore, yeah I think your example still stands. Specifically, in the wikipedia article you linked this part:

By contrast, pipes, sockets and command-line arguments are communication mechanisms normally used between two separate programs.

To continue the original example, if your program just runs the HTML generation program and supplies user data via a command line argument then it need not be released under a compatible license. But on the other hand if you were to "copy and paste" the functions from that program into yours, it would need to be licensed under a compatible license.