Yes, UE4 is not FOSS as per GNU, it is open source in that you can see the code and there's a large community contributing fixes and additions with every new version. I think the distinction is pedantic for most users.

"Source-available" seems to be the preferred term for what UE4 is.

> I think the distinction is pedantic for most users.

In a technical discussion, there's no reason not to use the proper terms for things.

> I think the distinction is pedantic for most users.

The distinction is that the code you write belongs to Epic. You become an unpaid contractor.

The Open Source Definition doesn't come from the Free Software Foundation or "GNU". It's a separate organization.[1].

Also the whole point of this story is that license terms do matter, especially if you want to sell games commercially.

[1] https://opensource.org/osd-annotated

I think the distinction is pedantic for most users.

Isn't Unity similar in that regard? (well, as far as viewing the source-code, they don't accept patches to my understanding)

https://blogs.unity3d.com/2018/03/26/releasing-the-unity-c-s...

That's just the C# code; not the native C++ bits which are the core of the renderer and engine.

UE4 is open to every last bit.

No, the amount of unity released is tiny.

You're wrong, users of software libraries care whether they're allowed to fork the library or not.

Define fork. You can make your own custom version and share that code with anyone, and use it exactly as freely as the original version.

The reason it's not open source is the royalty clause, not lack of ability to see/edit/modify/fork the code.

Unitys C# code is also visible source

I missed that announcement, good for them, too little too late: https://blogs.unity3d.com/2018/03/26/releasing-the-unity-c-s...

Note that this is just the C# layer. The underlying C++ engine code is still only available under "call us" license terms.

Shared source isn't open source. You may have access to it, but you don't own it.