OpenOffice has only a meager number of IBM developers (I'm not sure if they still continue contributing). (adding security to the project, because if one company stops development, others will continue support). LibreOffice is also developed by developers from a large number of commercial companies, such as Red Hat, Collabora, Canonical etc. LibreOffice commit log, OpenOffice commit log. LibreOffice has much more contributions than OpenOffice. This means that all improvements made in OpenOffice are available in LibreOffice but improvements made in LibreOffice are not available in OpenOffice. LibreOffice can reuse code from OpenOffice, while the opposite can't happen.

Most of the existing OOo developers jumped ship to LibreOffice, considering it the true continuation of OOo instead of Oracle OpenOffice, which was later donated to the Apache Foundation, becoming Apache OpenOffice. When Oracle bought Sun and threatened the existence of the office suite, a community fork was created called LibreOffice. Historical note: Until 2010 there was only one suite, (OOo) developed by Sun.

Openoffice vs libreoffice 2016