The Katalix Systems OpenL2TP software is Dual Licensed.  Users can
choose to use the OpenL2TP software as an Open Source/Free Software
product under the terms of the GNU General Public License
(http://www.fsf.org/licenses/) or can purchase a commercial license
from Katalix Systems Ltd.

The OpenL2TP software is released under the GNU General Public License
(GPL). This means that the OpenL2TP software can be used free of
charge under the GPL. If you do not want to be bound by the GPL terms
(such as the requirement that your application must also be GPL), you
may purchase a commercial license for the same product from Katalix
Systems Ltd.  Since Katalix Systems Ltd owns the copyright to the
OpenL2TP source code, we are able to employ Dual Licensing, which
means that the same product is available under GPL and under a
commercial license. This does not in any way affect the Open Source
commitment of Katalix Systems Ltd.

Users cannot change the vendor string which is published in the L2TP
control message protocol without purchasing a commercial license. For
all GPL installations, the vendor string shall be "Katalix Systems
Ltd. Linux".

The OpenL2TP software is released under the GNU General Public License
(GPL). The formal terms of the GPL license can be found at
http://www.fsf.org/licenses/.  See also
http://www.fsf.org/licenses/gpl-faq.html.

The GPL license is contagious in the sense that when a program is
linked to a GPL program, all the source code for all the parts of the
resulting product must also be released under the GPL. If you do not
follow this GPL requirement, you break the license terms and forfeit
your right to use the GPL program altogether. You also risk damages.
You need a commercial license under these conditions:

- When you link a program with any GPL code from the OpenL2TP software
  and don't want the resulting product to be licensed under GPL,
  perhaps because you want to build a commercial product or keep the
  added non-GPL code closed source for other reasons. When purchasing
  commercial licenses, you are not using the OpenL2TP software under
  GPL even though it's the same code.

- When you distribute a non-GPL application that works only with the
  OpenL2TP software and ship it with the OpenL2TP software. This type of
  solution is considered to be linking even if it's done over a
  network.

- When you distribute copies of the OpenL2TP software without providing
  the source code as required under the GPL license.

- When you change the advertised L2TP vendor string.

A special exception is made for OpenL2TP plugins. Such plugins may be
closed source and not come under GPL provided that they use OpenL2TP's
standard plugin interface. It is not permitted to make open source
changes to OpenL2TP in order to add new interfaces to OpenL2TP and
then write a closed source plugin that uses the new interface.

If you require a commercial license, you will need one license for
each installation of the OpenL2TP server software. One license is
required for each CPU / memory subsystem that runs OpenL2TP
binaries. Multiple CPU "Symmetric Multi-Processor" (SMP) systems
require only one license per SMP CPU group.

OpenL2TP uses an implementation of MD5 Message Digest Algorithm by RSA
Data Security, Inc.

