In short, Air Video is a client-server product that streams, via live conversion, videos of many formats to any iOS device (eg iPhone, iPad etc). The server software is free-of-charge but only runs on Mac OSX and Windows. The client is also free-of-charge for iOS devices but "crippled". If you like the solution, you pay for the client.
Since the Air Video Server is written in Java and uses a customized version of FFMPEG, it would be possible to run it on Linux. The folks behind Air Video though supportive but are NOT offering official support for Linux.
I have been successful in making Air Video Server (AVS) work on openSUSE 11.3, 11.4 and 12.1. Here are the steps: