Knowing Mozilla it is probably open though as guzzi says, there would have to be an operating system layer to interface with. There's also the question of what codec the video uses.
The other thing that has been added into recent releases is support for H264 video. Cisco is making a library available at
http://www.openh264.org/ and is covering the licensing costs if you download the binary from them (Firefox downloads the library when needed). Probably be easy to port but they'd have to build it which would mean that they'd need an OS/2 license and script to build it.
There's a good chance that Firefox Hello uses H264 as it is supported in hardware on most platforms including mobile where using hardware decoding uses much less power.
As usual it is having the developers to develop and we don't have many and the ones we do have are busy. I'd just like to have an up to date, stable browser.