There are quite a few projects out there already in both camps but I was wondering what are the pro/cons and business models used with open source game engines. If you work on an engine and just focus on that then youre not going to be in a good position to make direct revenue from it, vs. marketing a closed source engine (which in its own right is probably near impossible). So it would seem that your only option for an open source engine is to make a product with it and sell that. From what I can gather the most beneficial thing you get from an open source project is additional manpower. You do get better testing and sometimes you get patches submitted to fix problems. However relying almost exclusively on a community of independent, unpaid developers to bring a product to market sounds kind of crazy, but some have done it. For example the Blender foundation business model includes selling books, short movies and donations. Seeing that they have not gone under it so would seem that this models works. However they are understaffed and the project is so massive that they do have a hard time keeping up with it. So it would be nice to get some input on the subject.