libusb-1.0.9 and libusbx-1.0.11 have OpenBSD/NetBSD support. Now libusb-1.0 and libusb-compat are OpenBSD's ports system. NetBSD's pkgsrc system (okay, pkgsrc is not only for NetBSD) now has both libusb-1.0.9 and libusbx-1.0.11, it also has libusb-compat as well.
On the other hand, at least for the faster moving libusbx,
OpenBSD/NetBSD are behind the other supported OS (Linux,
Mac OS X and Windows). Hopefully the OpenBSD/NetBSD users
can jump in and bridge the gap.
Take note FreeBSD has its own libusb-1.0/libusb-0.1 wrapper
on top of its own libusb20 library.