ZeroTierOne/LICENSE.txt

ZeroTier One - Network Virtualization Everywhere
Copyright (C) 2011-2017  ZeroTier, Inc.  https://www.zerotier.com/

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.

See LICENSE.GPL-3 for the full GNU GPL v3 license.

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You can be released from the requirements of the license by purchasing
a commercial license. Buying such a license is mandatory as soon as you
develop commercial closed-source software that incorporates or links
directly against ZeroTier software without disclosing the source code
of your own application.

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The above license does not apply to third party code included with or
linked against by ZeroTier software. See the third party code section
of the AUTHORS.md for an index of third party software included in
this software repository.

Licenses for third party code are all relatively permissive: MIT,
BSD, and public domain. The only exception is the tap-windows driver
which is under the GPLv2, but this is only needed to produce the
binary tap device driver used by the ZeroTier service on Windows.