This project uses Mercurial to manage its source code. Instructions on Mercurial use can be found at http://hgbook.red-bean.com/read/.
The source can be checked out anonymously from Mercurial with this command (See http://www.selenic.com/mercurial/hg.1.html#clone):
$ hg clone http://olog.hg.sourceforge.net/hgroot/olog/olog-java-api