Trunk version means, it is in development. Day by day all the milestone features and existing bugs will be reduced. After some point it will be tagged as version x.x. Trunk is repo name used by launchpad, but now odoo (openerp) project has been moved to github it will called as master. The next stable version will be released on July 7, 2014 (SaaS) as far as i know.

You can download master and all previous stable from github and launchpad....
Project Url for Github     Project Url for Launchpad
Download link...

Yes, you can use all the addons in your server. For more License...

It means i need to download developer verison from trunk folder.

One more question,

Can i install all available apps in my own server?

thanks