If you can't find a way to get GRIP to work on the Pi, you can try what we did. The GRIP installation instructions for the Pi weren't figured out yet, so instead of trying to figure it out or wait for instructions, we went with OpenCv directly.
Here's the install for Raspbian
Open CV Install (takes 4hrs to complete)
We then installed PyNetworkTables to communicate to DriverStation.
If you need to stream the image, we used mjpeg-streamer.
Our image processing code was written in Python. PyImageSearch.com has a but of help for Python & OpenCv.
PM me if you need more help.
Brian