Not sure it's been tried. I'm betting the current version can't, since it's handling enabling and connecting to the bluetooth device itself. There are older versions that talk to a serial port, assuming you've already setup the port for it (be that bluetooth or serial). It probably wouldn't take a lot of work to change the code, but the maintainer has long since dropped not only this project, but the device line as well.

On the up-side, there are lots of other open-source tools for using usb-based dongles. If you can find some that are python or pearl based, they should work fine on the N900 with minor changes.