Now, that UE4 is free, why is it still a private repository on GitHUB?

[qdelpeche]

Because although it is FREE it is NOT Open Source and you still have to have an account in order to access it.

The account indicates your acceptance of the EULA and allows Epic to control access to the engine which is FREE for license holders but NOT Open Source.

UE4 EULA

Epic grants you a non-exclusive, non-transferable, non-sublicensable (except as described in this Agreement) license for a single User to use, reproduce, display, perform, and modify the Licensed Technology for any lawful purpose (the “License”). However, the rights that Epic grants you under the License are subject to the terms of this Agreement, and you may only make use of the License if you comply with all applicable terms.

The License becomes effective on the date you accept this Agreement or download the Engine Code or any Content. The License does not grant you any title or ownership in the Licensed Technology.

You may only Distribute Licensed Technology as follows:

a. Distribution to end users - You may Distribute the Licensed Technology (including as modified by you under the License) incorporated in object code format only as an inseparable part of a Product to end users who are subject to an end user license agreement which explicitly disclaims any representations, warranties, conditions, and liabilities related to the Licensed Technology. The Product may not contain any Engine Tools.

b. Distribution to other licensees - You may Distribute Engine Code (including as modified by you under the License) in Source Code or object code format, or any Content, to an Engine Licensee who has rights under its license to the same Version of the Engine Code or Content that you are Distributing.

Any public Distribution which includes Engine Tools must take place either through the Marketplace (e.g., for distributing a Product’s modding tool or editor to end users) or through a fork of Epic’s GitHub UnrealEngine Network (e.g., for distributing source code).

You also may Distribute Content to an Engine Licensee who is your employee or your contractor regardless of whether they have rights under their license to the same Content, but only to permit that Engine Licensee to utilize that Content in good faith to develop a Product on your behalf for Distribution by you under the License, and not for the purpose of Content pooling or any other Distribution or sublicensing of Content that is not permitted under this Agreement. Recipients of such a Distribution have a limited license to use, reproduce, display, perform, and modify that Content to develop your Product as outlined above, and for no other purpose.

c. Distribution and sublicensing of Examples - You may Distribute or sublicense Examples (including as modified by you under the License) in Source Code or object code format to any third party. However, the rights in this Section 1(c) do not expand or modify your limited Distribution and sublicensing rights for Engine Code and Content (including as modified by you under the License) that are not Examples.

d. Distribution of Non-C++ Programming Language Integration - You may Distribute an integration of a programming language other than C++ for the Licensed Technology, but if you do, the integration must be Distributed free of charge, permit Distribution in a Product free of charge on all platforms, and be available in source code form (including, but not limited to, any compiler, linker, toolchain, or runtime) to all Engine Licensees.