I installed Odoo version 8 on OS X 10.10.5 Yosemite through git repository, and play some of modules, and try to adapt simple purchasing process into Odoo. I usually run odoo.py script to start Odoo.I would like to use currency_rate_update module, which should check currency periodically as cron job. However, the cron job never run.

I notice from several Q/As in this forum also has example to start Odoo from openerp-server or openerp-gevent script. I used both and the database drop down list dont show up. I also cant login to my previously created database, or new database I created with Odoo started via openerp-server. I would like to show the database, because I set up 2 databases  for Odoo, one installed with demonstration data and the other is clean database.

So how to run Odoo properly from source?

--Edit--

What is the difference between starting Odoo using odoo.py, openerp-server, and openerp-gevent? Why if I use odoo.py the database list appear on login page, while using openerp-server the database is disappear on login page?