So now having read a bit more about this whole thing. The GPL restrictions do seem quite similar to what the NPSL have, related to Derivative Works, have a look at this from the FSF website[0]: """ What is the difference between an “aggregate” and other kinds of “modified versions”? ... By contrast, pipes, sockets and command-line arguments are communication mechanisms normally used between two separate programs. So when they are used for communication, the modules normally are separate programs. But if the semantics of the communication are intimate enough, exchanging complex internal data structures, that too could be a basis to consider the two parts as combined into a larger program. """
This does seem quite similar to what the NPSL does when it mentions software that calls and parses data from NMAP, the difference being that the GPL is not as explicit about it (it's a bit vague, probably on purpose), although FSF states clearly that something like a shell script that calls a binary and uses its output could fall into Derivative Works. The DFSG item 9 is also more about contamination by means of distribution other than interaction between the tools, as it says: "The license must not place restrictions on other software that is distributed along with the licensed software. For example, the license must not insist that all other programs distributed on the same medium must be free software." Considering both things, I'm inclined to say that the license is DFSG-compliant. Does this change your mind, Hilko, or are you still in the same position? I'll try to get somebody else's opinion on this as well, maybe someone from the ftp-master team could help. [0] https://www.gnu.org/licenses/gpl-faq.html#MereAggregation -- Samuel Henrique <samueloph>
