Since Kendy's blog has somehow disappeared from Planet KDE, let me copy&paste one entry (http://artax.karlin.mff.cuni.cz/~kendy/blog/archives/monthly/2009-06.html#2009-06-15T14_37_23.htm):

Thanks to the heroic efforts of Éric Bischoff, Bernhard Rosenkränzer, and Roman Shtylman, the OpenOffice.org KDE Integration has been ported to KDE4. It still has some rough edges (currently the detection does not work out of the box—you have to export OOO_FORCE_DESKTOP=kde4 to get it), but it is safe because it co-exists nicely with the existing KDE3 integration; so if you are not satisfied, you are able just swich back to KDE3 (export OOO_FORCE_DESKTOP=kde).

For KDE4, Roman is also changing the out-of-process implementation of the KDE file picker to an in-process implementation, so you'll probably notice some performance improvement of the KDE file dialog launch too :-)

End of copy&paste. For people who'd be interested in helping with this, I've been told those should join #go-oo on Freenode.