Translations are contributed by the community. They are managed on the translation website http://www.ransifex.net
. When a translation reaches a certain point (I think 50% completion), we include it in the main civicrm-l10n.tar.gz. In the mean time, it is also possible to get the "civicrm.mo" file from the github repository: https://github.com/civicrm/l10n/tree/master/po/fa_IR
The Persian translations seem to not have been updated in a while. Also, strangely there is a "fa" translation, but also a "fa_IR" translation, and both have a very little activity:
* fa: https://www.transifex.com/projects/p/civicrm/language/fa/
* fa_IR: https://www.transifex.com/projects/p/civicrm/language/fa_IR/
The language code "fa" versus "fa_IR" indicates that fa_IR is a regional translation specific to Iran. For example, we also have fr_CA or es_MX. However, in general, I would recommend to converge as much as possible towards one translation, since translating CiviCRM is a huge task.
In short, you can create an account on transifex.net, join the fa_IR team, say hi to the current team coordinator and see if he is still actively translating. You can export the translation files from transifex (.po -> .mo), but it may be easier to wait one night and it will be merged into the github repository. Once a week (saturday, I think), the civicrm.mo is re-compiled in the github repo.
I also encourage you to create a "lexicon" for the Persian language. This will help a lot to help translators to translate terms in the same way. Otherwise, a "contact", for example, might be translated in 5 different ways, and it can quickly become confusing:http://wiki.civicrm.org/confluence/display/CRMDOC43/Translator+resources