libusb is a library for USB device access from Linux, Mac OS X, Windows, OpenBSD/NetBSD and Haiku userspace. It is written in C (Haiku backend in C++) and licensed under the GNU Lesser General Public License version 2.1 or, at your option, any later version (see COPYING).
libusb is abstracted internally in such a way that it can hopefully be ported to other operating systems. Please see the PORTING file for more information.
libusb homepage: http://libusb.info/
Developers will wish to consult the API documentation: http://api.libusb.info
Use the mailing list for questions, comments, etc: http://mailing-list.libusb.info