Open-source and Epic's source code availability

Community Community & Industry Discussion
1

With the latest news about Epic removing the subscription cost for UE4, we are seeing a lot of new developers jumping in with excitement, to see what they can create. This is going to be a busy time for many, but I feel that there is something that needs to be clarified. It’s about the source code for UE4, which has been brought up quite a bit in the last few days.
So, here’s a question for you:
What open-source license is UE4 under?
A) BSD
**B) **Apache License 2.0
C) GNU General Public License (GPL)
D) MIT license
E) Mozilla Public License 2.0

Answer: None of the above. That’s because it is a trick question.

EPIC did not make UE4’s source code, “Open Source”. What they did for all of us though was make the source code available to look at, modify, fix, twist, turn, and prod to our hearts content. Because of this, we have the ability to submit fixes for problems that we come across, and can, after review, see them added to the source code for everyone.
We can come up with new ideas that could be added directly into the engine, and be able to test it out in our own forks. If we want, we can submit them to Epic to be included in the future, with them giving credit to those that do this work. You are also not required to give Epic anything you have added to your own fork of the code. There is no requirement do to so, unlike many of the “Open Source” licenses.

Please remember this distinction, as we are seeing too many people keep calling this an open-source engine. In my own head, I’ve pretty much always called it, “Available Source”, because that is the difference. It’s available to us. The source code doesn’t belong to the people, and it doesn’t belong to the public masses. The source code belongs to EPIC, and they have given us the ability to use, read and learn from it, which is incredible. Thank’s again EPIC for this great opportunity.

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I think people misunderstanding “open-source” with “free software” and by free it means Stallman’s idea of free which you talking about and in my opinion connecting the two only confuses people. Open source should mean there open access to source, which UE clearly has, the difference is redistribution and use of source code, Free software licences let you copy source to your own project, you can’t do that with UE4, you can’t also redistribute it (but you can distribute you own code modifications (but not full files) and your classes as you like)… which at that point actually licences you mention differs a lot, for example with BSD or MIT i can modify the code i can copy it but i don’t need to open the source of my modifications, thats why some GPL fanatics considers GPL as only legit free software licence, because free software is practically a ideology, GPL was designed like virus to infect other projects with it so it can create world of free software and thats why some companies, even thru they wish there software source to be open they avoid GPL like a plague :stuck_out_tongue: Thats also why you can’t mix GPL software with UE4

3

If you want to go full RMS (never go full RMS), it’s free-as-in-beer. People were calling this engine open source back when it released last year when it cost $20/m so not much has changed.