Can’t you update owncloud, I’ve read that you have to install a newer PHP Version, a howto for installing newer PHP is here:
http://community.nethserver.org/t/need-tests-nethserver-php-scl/728?u=apradoc&source_topic_id=3768
Edit: I’ve installed 6.8 to test it, but at this time update php-version didn’t work for me.
Perhaps @stephdl can help. Owncloud should run at Cent OS 6.8 with newest PHP Version, but I don’t know if there are problems with other nethserver modules.