It looks like your Grunt is built using the unixODBC library instead of the competing iODBC library. While unixODBC is very common on Linux, iODBC is the de facto standard on OS X (it was the only pre-installed option on OS X from 10.2 to 10.8, so nearly all commercial applications and drivers use it).
The two libraries have basically the same API but are not interchangeable. The FileMaker ODBC driver is built using iODBC, so the Grunt application will need to be built using iODBC.
Actual Technologies - ODBC for OS X