What does the Unity license say about making a game engine with Unity?

I imagine you could make a Unity game that for example had c# code that compiled python code that the user typed to make a game.

You might want to do such a thing to take advantage of some of the Unity features such as skinned meshes etc. rather than building a game engine from scratch.

Or you could make a game like Roblox which allows users to make their own mini-games.

But (I would assume) you couldn't make a near enough clone of Unity using Unity, and some kind of reflection in c# so the user would be able to access all the Unity API. And then call it Boonity.... or could you?

For example consider these cases:

1) Allow user to write simple python code that moves spheres and cubes around in a game loop.
2) Allow user to write c# code that accesses the MonoBehaviour class using reflection.
3) Allow the user to upload 3d models to their mini-game which uses the SkinnedMesh class and allow the user to access the SkinnedMesh API using c# reflection.
4) You bundled MonoDevelop with your game and you game looked like an IDE which makes games.
5) You replicate the entire UnityEngine API but changed the names of all the methods and class names.

At what point are you stepping beyond the bounds of just allowing your user to make mods/mini-games and actually just allowing the user to use Unity functionality by circumventing the license?

Just curious about this meta problem.

 

I don't remember how they phrased it, but you can't create anything that "competes" with the unity engine in any way.

 

Well that's not very clear. I mean a hamburger competes with the Unity engine in terms of things you can buy for your money.

On the other hand Unity studios has released some demo games. So by that reasoning you can't use Unity to make games!

 

Don't be obtuse. A game engine made in Unity directly competes with Unity, the game engine.

 

2.6 General Restrictions.
Except as expressly specified in this Agreement, you may not: (a) copy (except in the course of loading or installing) or modify or create derivative works of the Unity Software; (b) distribute, transfer, sublicense, lease, lend, rent or otherwise provide access to the Unity Software to any third party; (c) directly or indirectly make the functionality of the Unity Software available to multiple users or third parties through any means, including but not limited to by uploading the Unity Software to a network or file-sharing service or through any hosting, application services provider, service bureau, software-as-a-service (SaaS) or any other technology or service; (d) use the Unity Software for competitive analysis or to develop a competing product or service; or (e) do anything that could cause or result in the Unity Software (including the runtime portion thereof) being subject to any open source license (or similar license) that requires as a condition of use, modification or distribution that the Unity Software (including the runtime portion thereof) or other software combined or distributed with the Unity Software be: (i) disclosed or distributed in source code form; (ii) licensed for the purpose of making derivative works; or (iii) redistributable at no charge. You acknowledge and agree that portions of the Unity Software, including but not limited to the source code and the specific design and structure of individual modules or programs, are confidential and constitute or contain trade secrets of Unity and its licensors. Accordingly, you agree not to disassemble, decompile, modify or reverse engineer the Unity Software, in whole or in part, or permit or authorize a third party to do so, except to the extent such activities are expressly permitted by this Agreement or by law notwithstanding this prohibition. Notwithstanding the restriction prohibiting decompiling in the immediately preceding sentence, you may decompile the Unity Common Language Infrastructure (CLI) assemblies solely to inspect their functionality for purposes of understanding or improving performance of your Project Content or any editor extension to the Unity Software.


when in doubt - go read the eula or contact unity directly

 

Beyond the legal text, I'd ask myself if your product didn't exist would any of your customers use Unity instead? If the answer is "yes", then you're making a competing product which would not be allowed.

How this differs from a mod, is generally people make mods because they want new adventures within the existing game, not because they want to create an entirely new game.

IANAL

 

At the point where you no longer require the original product in its original form. Enderal, for example, is a total conversion of Skyrim yet like any other mod it requires Skyrim to be playable.

https://sureai.net/games/enderal/

Simply creating a game engine that sits on top of Unity isn't competition. What makes it competition is if the user of your engine doesn't need a license for Unity. If the user has to have Unity to be able to use your game engine then your game engine is simply an extension of Unity.

Corgi, for example, states that it is an engine on its own website yet it's perfectly legal because you still need Unity.

https://corgi-engine.moremountains.com/

IANAL