Joint Copyright Assignment
From Apache OpenOffice Wiki
The Joint Copyright Assignment
This lurks here (pdf).
A non-lawyers view of this & it's reasonable-ness is provided by Michael Meeks (a non-Sun developer):
In my opinion the JCA is both sensible and reasonable. 1st - it is important to have a single owner for the OO.o codebase copyright to allow re-licensing in future. Ideally it would be owned by a neutral 3rd party, but the existing situation works well because: 2nd - Sun does not (ab)use the re-licensing provisions available to them, indeed - quite the opposite they contribute all their changes to the code following the spirit of the LGPL much as anyone else would. Furthermore, the JCA doesn't 'loose' you your copyright, just shares it. Novell, RedHat and other corporations & groups have collectively signed the JCA.
There is more good blurb about this [1] here for those that want to know more.