Repo --> https://github.com/zerotier/ZeroTierOne
Web page: https://www.zerotier.com
It is. open source
The ZeroTier source code is open source and is licensed under the GNU GPL v3 (not LGPL). If you'd like to embed it in a closed-source commercial product or appliance, please e-mail email@example.com to discuss commercial licensing. Otherwise it can be used for free.