Hi,
I had to deal with the "custom packages" issue building custom system on top of ACS working for http://www.competitiveness.com/ . We checked with some lawyers in Barcelona, Spain and Boston, US, and the key legal question seems to be the exact definition of "derived work".
The GPL says: "You must cause any work that you distribute or publish, that in whole or in part contains or is derived from the Program or any part thereof [...]":
=> If you don't "distribute", you can do whatever you like.
=> A module that you have written from scratch does not "contain" GPLed code.
=> "Derived from" was interpreted by our lawyers as "other strange ways to include GPLed source" to prohibit for example the use of decompiled binary code etc.
So we have built several customer systems without worrying about the licence question. I would be happy to get challenged on this...
Additionally, please keep in mind that the GPL has not been tested in court yet, neither in the US nor in Europe. We all may get very surprised if SCO/Microsoft manages to succeed with their fud fight against Linux.
Worse: A recent analysis in Germany (http://www.vsi.de/inhalte/aktuell/studie_final.pdf) shows that the GPL is probably not enforceable under German law. Spanish law is even less restrictive, resulting for example in huge problems for the RIAA to close MP3 servers here...
So today it is highly unlikely that you have to suffer any consequences from violating the GPL, other than a bad "karma" in certain Open-Source communities... 😊
Bests,
Frank
mailto:fraber@fraber.de, http://www.fraber.de/
