I have some good news in regard to figuring out what’s the problem.
Apparently, libusb_reset_device() sometimes executes certain operations which require privileges beyond having access to the /dev/usb/* device node entries. Running every program as root seems to “fix” the problem (granting access to the device nodes does not), but isn’t a practical solution.
I wonder if FreeBSD’s libusb should (and/or could) be fixed to ensure libusb_reset_device() can be run as non-root user, or if the Lime Suite should be fixed to not call libusb_reset_device() at all because it might be an administrative call that should never be used by a user of a USB device. I’m not sure what’s right to do. Particularly, I don’t know why the Lime Suite developers included that call, and I don’t even fully understand (yet) what it does.
The discussion with the FreeBSD community is going on on the freebsd-usb mailinglist, in case you want to follow up on our discussion there. Some helpful hints from the Lime Suite developers would be appreciated on the list (or on this forum, as I can also forward hints posted here).
In addition to the problem with access rights as non-root users (despite having access to the particular device), there seem to be some timing errors (see my original post on top of this thread). I wonder if it’s possible to provide the FreeBSD USB community with a free sample in order to figure out what’s wrong. I think it would also be in the best interest of the manufacturer to get FreeBSD support this device properly (as well as it’s a gain for the FreeBSD community to be able to support such an amazing device!).