2007.07.16 11:51 "Re: [Tiff] [ANNOUNCE]: Libtiff 4.0.0alpha released", by Graeme Gill

So what happens if someone builds a standalone piece of s/w (tiffjbigdecomp) that reads (compressed) data from stdin and writes (uncompressed) data to stdout. They can then write s/w that execs a sub-process, redirecting stdin/stdout to be a file on disk and a pipe, and then just read the decompressed data from the pipe. Does that infringe GPL?

Not if you don't distribute it no. Package it up with a particular purpose in mind with code that isn't distributed under the same terms as the GPL and copy it, and you aren't complying with the GPL since the package is a derived work, and copyright applies to derived works.

 > I think not (as otherwise no commercial s/w could run on

Linux), in which case I think the claim that dynamic loading / linking does (infringe GPL) is not necessarily solid, as the difference between that and dynamic linking to a library is pretty thin.

It's not a matter of running, it's a matter of copying. And there are specific exceptions in the GPL for distribution with standard operating system components, "mere aggregation on the same media", linking with standard GPL library components, and in the Linux version of the GPL there is an exception that permits software that uses the Linux kernel via the user/kernel interface to be compliant (at least in stuff from Linus). There's certainly nothing to stop an end user combining GPL and non GPL components in any way they want to achieve an end ("running" is permitted), but it may be impossible to distribute ("copy") such combinations together and be compliant with the GPL.

By default copyright says two copyrighted works aggregated together is a derived work of both, and the GPL only makes an exception for the case of aggregation where it is merely a means of distributing things that are otherwise independent.

Graeme Gill.