I was recently asked whether or not it was more effective to start out a 3D Online RPG engine by creating all of the engine pieces from scratch, or use already created free, open-source libraries. These pieces include a graphics rendering engine, networking engine, audio engine, physics engine, content engine, and each of these component's sub-parts.
The project in question was to be a small 3D Online RPG game that would be released to the public for free yet have a monthly subscription fee.
So the questions I have are:
Do free, previously coded and open source game engine libraries usually allow their creations to be used in projects that charge a monetary, monthly fee for their products?
Are these free open source game engine libraries easily integrated and combined with each other in a project?
Thanks in advance!