Marc Egli writes:
Ok but i can add a script to Mailman which accepts a path to a mail file, then reads that file and gives a csv list back.
Yes, I would think so. The FSF likes to bluster that programs running in separate processes that interact with each other via standard interprocess channels (eg, stdio) could be considered a single work under copyright law, but I don't see how. The calling program never contains a physical copy of the GPLed code (or a derivative such as a compiled and partially linked DLL).
In the case of the GPLed script you're talking about, you don't use the Mailman code code it's based on in your application, you use its output. The GPL explicitly disclaims any restrictions on the output. Furthermore, it seems to me that your script would be independently useful to folks like Mark Shapiro who support users whose bounce processing seems wonky; it's clearly a separate work, not part of your application.
Since your earlier proposal is functionally equivalent to this, it would be nice if the GPL could somehow allow you to avoid the fork tax. But I don't think it can; copyright ends as soon as you allow someone to make a copy, you can no longer control the use of the copy. So this would probably be a huge loophole for abuse of GPLed plugins.
Again, IANAL, so you could ask the FSF to be absolutely sure. RMS and his lawyers are quite scrupulously honest about this; they will happily tell you that your use is permissible if it is (and equally happily go on to tell you that you really ought to be using GPL for your own work<wink>).