Copyright (c) 2018, Valve Corporation
All rights reserved.

Redistribution and use of Proton in source and binary forms is governed
by a variety of licenses.

Refer to the contents of LICENCE.proton for the license for the top
level contents of the Proton project.

Proton uses a variety of other software, each of which is governed
by its own license.  Those licenses are contained in a file named
LICENSE or COPYING in each directory.
