Section 7:

All other non-permissive additional terms are considered “further restrictions” within the meaning of section 10. If the Program as you received it, or any part of it, contains a notice stating that it is governed by this License along with a term that is a further restriction, you may remove that term. If a license document contains a further restriction but permits relicensing or conveying under this License, you may add to a covered work material governed by the terms of that license document, provided that the further restriction does not survive such relicensing or conveying.

I don't think it's enforceable, but IANAL.

What prevents them from just using the parts of the GPL they want?

>Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed.

Somewhat ironically, the reason for this is that the FSF holds the copyright to the GPL, so only they can change it. Well, you could probably change it, but you couldn't call it the GPL anymore... and it would probably be copyright infringement.

I wonder what would happen if the GPL itself was licensed under the GPL... I suspect it would start raining turtles. :)

According to their FAQ you can change it, but you have to change the name and remove the preamble entirely.

The GPL was devised as a way of turning Copyright against itself.

From that FAQ: "If someone asks you to sign an NDA for receiving GPL-covered software copyrighted by the FSF, please inform us immediately by writing to [email protected]."

Also from that FAQ: "If the violation involves GPL-covered code that has some other copyright holder, please inform that copyright holder, just as you would for any other kind of violation of the GPL."

FYI: VoltDB owns the copyright to the code.

Right.... So it's probably perfectly binding. If they hold the copyright outright, they can create such conundrums lik e conflicting licenses. If it incorporates the work of others though , it's tricky.

Looks to me like it's carefully worded to be a non-binding NDA--they "ask" that you not redistribute the source, but they don't provide the code solely upon receipt of that promise, or threaten any penalties for it.

As far as I know, it's both legal and meaningless to ask for anything you like.

Legally, probably not. They aren't demanding that you not redistribute, just asking. And asking politely. They are banking on the good nature of people. Good for them! And us.

Exactly. The Condor Project did this for many years and, miraculously, every one of the hundreds of users to whom we gave the source respected the request and the source never leaked. (It is now fully open.)

If they don't want people to redistribute the code, why on earth are they GPL'ing it?

I can't speak for them, but in our case we had major users who required open-source (mostly European govt. projects).

All our developers wanted to just post the source online and be done with it, but our boss had security concerns he wanted us to address first -- so in the meantime we gave people who needed it GPL'ed copies, and asked them politely not to redistribute until we were ready.

Probably not, but if people start disrespecting their wishes, and the code is all their own (that is, does not include other parties' GPL'd code), then they can simply change the license and get the same effect.