Of course you can use owncloud with the MBL. Use this tutorial to set it up.
http://community.wd.com/t5/My-Book-Live/GUIDE-Installing-OwnCloud-Server-on-My-Book-Live/td-p/561699
You will notice that the owncloud installation may call for php5.4, which is not something the orginal guide had to deal with. You will need to edit your sources.list to get the Weezy feeds. Put these in and edit out the other feeds.
deb http://ftp.us.debian.org/debian/ wheezy main
deb-src http://ftp.us.debian.org/debian/ wheezy main
Then do the installation again.
OR if you want to use the guide to install the version of owncloud which was avalible when the guide was written, use this work around
