libusb-1.0 is an almost-rewrite of the previous stable branch,
libusb-0.1. It is a lightweight library that can be efficiently
integrated into applications of any kind, with several new features.

Backwards compatibility
libusb-1.0 is not backwards compatible with libusb-0.1 - all function
names are different, etc. However, libusb-1.0 is designed to be happily
installable alongside libusb-0.1 (even in the default configuration) so
the lack of backwards compatibility is not really a problem - users can
have both libusb versions present on the same system without conflict.

That said, a libusb-compat-0.1 compatibility layer does exist. This
is a "wrapper" which converts libusb-0.1 function calls to their 1.0
equivalents. For more info, see LibusbCompat0.1.