GLFW is licensed under thezlib/libpng license,a BSD-like license that allows static linking with closed source software. Itis reproduced in its entirety below.
Copyright © 2002-2006 Marcus Geelnard
Copyright © 2006-2019 Camilla Löwy
This software is provided ‘as-is’, without any express or impliedwarranty. In no event will the authors be held liable for any damagesarising from the use of this software.
Permission is granted to anyone to use this software for any purpose,including commercial applications, and to alter it and redistribute itfreely, subject to the following restrictions:
The origin of this software must not be misrepresented; you must notclaim that you wrote the original software. If you use this softwarein a product, an acknowledgment in the product documentation wouldbe appreciated but is not required.
Altered source versions must be plainly marked as such, and must notbe misrepresented as being the original software.
This notice may not be removed or altered from any sourcedistribution.
You can find this license in the fileLICENSE.md of the GLFW source treeand in the comment header of each source file.