Many of the developers were already fed up with Sun's poor stewardship of the OpenOffice.org project, hence the go-oo project which hosted many improvements that Sun did not integrate and was the basis of OpenOffice packages that most Linux distributions shipped. Oracle was just the final straw that catalysed a true fork (go-oo was more of a patch set that needed to follow OOo). LO used the GPL because that was pretty much the only option (and maybe the developers think it is better for LO than a permissive licence). LO made big strides, for example in code clean up and build systems even before Oracle decided dump the code on the Apache foundation. The permissive was probably to keep IBM happy, as they have previously released closed derivatives of OO.
What code exactly have LO stolen from AOO? There is nothing new in AOO to be worth taking, LO has always been a step ahead of AOO (and is about 3 steps ahead now). The only possible example is the sidebar, but that was developed by IBM, not Oracle or Apache.
Personally I think Apache should de-list AOO on the grounds that they can't even produce security updates in a timely manor.