Information, Technology, Security, and other stuff.
My Brother-in-law had some problems running ImageJ with the Multispectral Image Calibration and Analysis Toolbox on his Mac.
Whenever he tried to open a RAW file for analysis, it would throw the error:
IO Error Executing System Command '-v'
It's not immediately obvious by the error message, but this is (as almost every problem in IT seems to be) a permissions problem.
The user account running ImageJ doesn't have execute permissions to run the dcraw plugin. Now you don't need to recompile dcraw to do this (despite some of the comments on forums), you just need to modify the permissions by running the following command in terminal:
chmod 777 /Applications/ImageJ/plugins/dcraw/dcraw
It may not need to be the maximum of 777 (perhaps only 660, I didn't experiment to see what was the minimum), but this should be sufficient to get it running.