The LUFA library is currently released under the MIT license, included below.

Commercial entities can opt out of the public disclosure clause in this license for a one-time US$1500 payment. This provides a non-exclusive modified MIT licensed which allows for the free use of the LUFA library, bootloaders and (where the sole copyright is attributed to Dean Camera) demos without public disclosure within an organization, in addition to three free hours of consultation with the library author, and priority support. Please visit the Commercial License link on Library Resources for more information on ordering a commercial license for your company.

Permission to use, copy, modify, and distribute this software
and its documentation for any purpose is hereby granted without
fee, provided that the above copyright notice appear in all
copies and that both that the copyright notice and this
permission notice and warranty disclaimer appear in supporting
documentation, and that the name of the author not be used in
advertising or publicity pertaining to distribution of the
software without specific, written prior permission.

The author disclaim all warranties with regard to this
software, including all implied warranties of merchantability
and fitness.  In no event shall the author be liable for any
special, indirect or consequential damages or any damages
whatsoever resulting from loss of use, data or profits, whether
in an action of contract, negligence or other tortious action,
arising out of or in connection with the use or performance of
this software.