This is the Syncthing project which pursues the following goals:
Define a protocol for synchronization of a folder between a number of collaborating devices. This protocol should be well defined, unambiguous, easily understood, free to use, efficient, secure and language neutral. This is called the Block Exchange Protocol.
Provide the reference implementation to demonstrate the usability of said protocol. This is the
syncthingutility. We hope that alternative, compatible implementations of the protocol will arise.
The two are evolving together; the protocol is not to be considered stable until Syncthing 1.0 is released, at which point it is locked down for incompatible changes.
Take a look at the getting started guide.
There are a few examples for keeping Syncthing running in the background on your system in the etc directory.
There is an IRC channel,
#syncthing on Freenode, for talking directly
to developers and users.
Building Syncthing from source is easy, and there's a guide. that describes it for both Unix and Windows systems.
As of v0.10.15 and onwards, git tags and release binaries are GPG signed with the key D26E6ED000654A3E (see https://syncthing.net/security.html). For release binaries, MD5 and SHA1 checksums are calculated and signed, available in the md5sum.txt.asc and sha1sum.txt.asc files.
Please see the Syncthing documentation site.
All code is licensed under the MPLv2 License.