Right to left languages have been supported in Moodle Core themes for the last several years and today there’s at least one contributed theme designed specifically to support Right to Left languages: Aaradyha.
RtL language support will orient the text and language in reverse when applied to the site, this can easily be done on any core theme by selecting a RtL language pack that’s installed, e.g. Farsi (find all available language packs for Moodle 2.4 here: http://download.moodle.org/langpack/2.4/). Installation can be handled directly through Moodle today via the Language Pack installer, As admin:
- Click site administration
- Expand “language”
- Select “langauge packs”
- Select which language and click “install selected language pack”
- This will make the language available from both the site default and course selection for languages.
To customize a non-core theme for RtL you can also refer to the theme documentation to help with your CSS and text orientation.
Note: I recently posted that RtL language support was a new feature coming to Moodle and I was mistaken; hope this helps to provide additional helpful information.