Have you tried as root? Maybe you miss some permissions.
I am currently attempting to use a raspberry pi to connect to the DRS 4 board. I whenever I try to use the DRS Command Line TOol, Revision 21435 to connect to the drs board, I get the error
"musb_open: libusb_open() error -3"
"USB successfully scanned, but no boards found"
"No DRS Boards Found".
I successfully compiled the libusb driver before compiling the drs software 5.0.6, and installed all other listed packages in the install instructions.