Hello everyone!

I have been developing a Game Engine with Editor for a few months now, and need a good license for it. I have been thinking and doing research for a while, and found 2 options which I think are best:

• One option is the MIT license, it's as open as it gets, gives users a lot of freedom, but doesn't give me a lot of freedom. E.g. What if someone takes my Engine and Editor, improves it, then sells it without releasing the source or under another license? That all that work might be for nothing, because someone else now has the same product with more features. But an upside of the MIT license is that it allows users to tweak it as they see fit, and it draws more users to my Engine and Editor.
• Another option is the Mozilla license, from what I've read it's similiar to LGPL/GPL, but doesn't require you to have a separate Engine(exe) and Game(so/dll) binary. The Mozilla requires someone else to contribute back to my project hen they modify something(I believe), which means they can't just run of with my Engine and Editor and sell it, because the exact source is already available for free. The downside to this though is that it might be too restrictive for people and drive people away(also because it's less known).

So the trouble I'm having is, I don't know which one to choose. I'm not a lawyer and I don't know much about it. I also don't have the money to hire one. So I here have a list of questions I hope you guys can answer:

1. Does the Mozilla license require every change made to the Engine/Editor by someone to be contributed back to the Engine/Editor? So let's say the Editor has a blue theme, and someone doesn't like it. He then forks or clones it and changes the colors to a grey theme. Is he now required to submit those changes back? Or is he just required to publish them in his own repository?
2. Does the Mozilla license require someone to contribute back at all? I mean, does it mean they have to contribute directly to my project, or does it just mean they have to publish their changes in a repository?
3. Can someone clone my source code and change the license? And can I do that with my own source?
4. Can the Editor and Engine be Mozilla/MIT licensed, and the Game be licensed differently?
5. Can someone just take my source with the Mozilla license and change the name, improve it, and keep it in a separate repository?(Not contributing back to me)
6. Will the Mozilla license drive people away?
7. Is the Mozilla license well known? What are some Game Engines with it?
8. Am I required to publish the source with either the MIT or Mozilla license?
9. Would you personally use a game engine and editor that uses a Mozilla license?(If you needed one)
10. Anything else important I might have forgotten?
11. What are some other downsides to the Licenses I forgot?

Thanks!

On 12/7/2018 at 12:12 PM, Tim Leijten said:

I'm not a lawyer and I don't know much about it. I also don't have the money to hire one.

Then you're not ready to release it the way you're describing. 

One of the major purposes of those open source licenses is that anybody can take it, make it better, and release it as their own. Anybody can "fork" a project to create their own based on yours, adopting your work and building a new product from it. This seems to be the opposite of what you are describing as your goal.

IP laws are much like a genie in a bottle. If you accidentally release it, it is impossible to recapture.

This kind of thing needs a chat with actual lawyers who understand the licenses and can take the time to understand your exact needs.  Most likely they will draft a license that exactly matches your requirements.  If you want to forbid other people from taking your product and re-launching it, none of the major Open Source licenses will work for you.

I get that impression based on the problems he had with each of the licenses and the questions he had:

On 12/7/2018 at 12:12 PM, Tim Leijten said:

all that work might be for nothing, because someone else now has the same product with more features. ... which means they can't just run of with my Engine and Editor ... He then forks or clones it and changes the colors to a grey theme. Is he now required to submit those changes back? ... Can someone just take my source with the Mozilla license and change the name, improve it, and keep it in a separate repository?(Not contributing back to me)

Combined, those statements lead me to believe his big fear is that someone will take his published work, improve on it, and leave him in the dust.

With open source software, all the licenses not only permit that type of thing, but for some it is explicitly an incentive to continue producing the best possible code. The Free Software Foundation has four "freedom" goals with the GPL and other licenses, and this ability comes with the fourth Freedom.

That is, anybody anywhere can can create a derived product, including marketing that product and charging a distribution fee for that product. They can do it without notifying you of their changes, nor incorporating their changes back into yours.

The fourth freedom means somebody else can start with the same product, add features and modify features, and supplant the original creator as the leader for the product.