I am thinking about developing my game and have a few questions. I am going to use these softwares and libraries : OpenGL, Visual Studio Express, GLFW. I have publishing and selling my game in plans. So my question is: is it possible to do that with these softwares? What common licenses are there and how to understand them clearly? I haven't done much research about it but I think that people that had experience with this kind of stuff may help.
If I have understood your question right, I believe you are asking if the tools you mentioned let you commercialize the games that you create using them.
In that case, the answer is yes. Their licenses and terms and conditions are very generous. Here's what they give you:
When it comes to OpenGL (licenced under MIT License)
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
When it comes to Visual Studio Express, their terms and conditions lets you commercialize your software. From the product information page:
Visual Studio Express products are available at no charge and may be used for commercial, production usage subject to the license terms provided with each product. For example, you can use Express for Windows to create apps that you can then submit for sale in the Windows Store.
GLFW From the GLFW licence page:
Copyright © 2002-2006 Marcus Geelnard
Copyright © 2006-2011 Camilla Berglund
This software is provided ‘as-is’, without any express or implied warranty. In no event will the authors be held liable for any damages arising 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 it freely, subject to the following restrictions: The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation would be appreciated but is not required.
Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
This notice may not be removed or altered from any source distribution.