Unwrap360 is a project mainly written in C++ and C, it's free.
Unwrap 360º Images taken with a mirror into a rectangular shape.
This simple application intends to be an on-the-road helper for transforming 360 degree images, taken with some sort of omnidirectional mirror, into rectangular images that can be viewed with 360 degree image viewers.
It currently does the work it is intended to do but: