LibreOffice will keep its name until Oracle decides whether it wants to donate the OpenOffice.org brand to the foundation, which in the meantime has invited Oracle to rejoin their new community by applying for membership. Initial supporters already include the Free Software Foundation, Open Source Initiative, Canonical, Red Hat, Novell, the GNOME foundation, and Google.
We can only assume that the forking is happening because OpenOffice's community is not sure how dedicated Oracle will be to the suite's continued development. The Document Foundation also hopes that LibreOffice's independence from Oracle will attract more contributors and lead to an even better product. Oracle became OpenOffice's principal contributor when it acquired Sun Microsystems earlier this year.