Current stable version is “ojs-stable-3_0_2” but a new stable will be released soon.
Yesterday I updated this post with git instructions, because is where google drives you when you search for “git ojs”:
(Thanks Clinton for the fixing in the version spelling 
)
In short, if you have git and composer installed, to get the last stable do this:
$ git clone -v --recursive --progress -b ojs-stable-3_0_2 --single-branch https://github.com/pkp/ojs.git /your/destination/path
$ cd /your/destination/path//lib/pkp
$ composer update
If it didn’t work, open a new post in forum, please. 