PHP 5.2.6 or higher, MySQL v5.0.41 or higher (mysqli), cURL installed on your server.
Server running Apache on Linux (Windows and IIS are not yet officially supported).
Recommended Joomla 2.5 updated to the latest release, also working on J1.5, J1.6, J1.7, J2.5 and J3.0.
Yup, Ohanah is and will be fully compatible with all the extensions built on Nooku Framework that stick to the Nooku release cycle.
(Unfortunately, at the moment, Ninjaboard is not updated to the latest stable Nooku Framework version, so this could create some temporary issues. Open a support request with them if you need to run both extensions on the same site, and ask them to provide you an updated version)
In theory yes, although it is almost impossible for us to test it with every template available out there. We do provide support for the most known and respected providers on the market.
For the time being we don't support Joomla backend-templates. We worked hard to provide the best UX for the backend without having to install any extra template.
Generally not, but we do have an awesome network of trusted professionals that just do this. They know the Ohanah codebase inside-out and they will be able to supercharge Ohanah with your own requirement.
Yes we do offer the best documentation for web developers available: just read through the Ohanah source code! Made with RESTful APIs that you can use, producing JSON for you to play with, and built upon leading edge Nooku Framework. If you are looking for dev support checkout our developer plan.