No, it has to be exclusive. Shared copyright doesn't work in practice. There is however nothing strange or unusual going on here, because FSF has the same solution for their contributors. The real problem here is that IP laws aren't well suited for open software.
/ Martin Nilsson (ja till euro, nej till cent)
Previous text:
2003-09-11 11:55: Subject: IDA's policy on Pike contributions
If I undesrtand this right, it basically means that I can't use my code anymore as I wish (and lose my copyright), once it is officially accepted and used in Pike.
In worst case, you can still use it under the MPL/GPL/LGPL like anyone else of course. It doesn't seem to say that the copyright has to be exclusive though. So i think shared copyright is ok, i.e. you keep copyright _and_ assign it to IDA, so that both may use it as they wish.
/ Marcus Comstedt (ACROSS) (Hail Ilpalazzo!)