Found ZLUDA very interesting. Don’t have an AMD graphics card, exactly because of CUDA. But would love to use a 16Gb+ 7000 series card 
I am not a programmer and don’t have the hardware, so can’t help you on the implementation.
But depending on your project you can experience nice speedups with a GPU.
There is a lot of info on the forum, but ultimately it depends on what you are planning to do.
Though it is absolutely NOT necessary to have a GPU to run ODM well. In fact there are still situations where I deactivate the GPU, for feature detection often anyway because of the memory limitations inside CUDA.
Here a post that maybe helps to get a picture of how the GPU is used and what effect it has:
The post is a bit “older” by now, but it mainly still works the same way.