RXTX License v 2.1 - LGPL v 2.1 + Linking Over Controlled Interface.
RXTX is a native interface to serial ports in java.
Copyright 1997-2007 by Trent Jarvi tjarvi@qbang.org and others who
actually wrote it.  See individual source files for more information.

A copy of the LGPL v 2.1 may be found at
http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html on November 21st 2007
A copy is here for your convenience.

This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.

This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
Lesser General Public License for more details.

An executable that contains no derivative of any portion of RXTX, but
is designed to work with RXTX by being dynamically linked with it,
is considered a "work that uses the Library" subject to the terms and
conditions of the GNU Lesser General Public License.

The following has been added to the RXTX License to remove
any confusion about linking to RXTX.   We want to allow in part what
section 5, paragraph 2 of the LGPL does not permit in the special
case of linking over a controlled interface.  The intent is to add a
Java Specification Request or standards body defined interface in the 
future as another exception but one is not currently available.


As a special exception, the copyright holders of RXTX give you
permission to link RXTX with independent modules that communicate with
RXTX solely through the Sun Microsytems CommAPI interface version 2,
regardless of the license terms of these independent modules, and to copy
and distribute the resulting combined work under terms of your choice,
provided that every copy of the combined work is accompanied by a complete
copy of the source code of RXTX (the version of RXTX used to produce the
combined work), being distributed under the terms of the GNU Lesser General
Public License plus this exception.  An independent module is a
module which is not derived from or based on RXTX.

Note that people who make modified versions of RXTX are not obligated
to grant this special exception for their modified versions; it is
their choice whether to do so.  The GNU Lesser General Public License
gives permission to release a modified version without this exception; this
exception also makes it possible to release a modified version which
carries forward this exception.

You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
All trademarks belong to their respective owners.

Continue reading LGPL2.1 here.