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

Someone mind to elaborate on this?

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

are you crazy man?

think about it.
you think we could keep this unyieldy beast under control?
you want a 1st grader uploading code, although they might could do a better job than I could.

no there’s reasoning behind it, first of all, we have access to the engine source but it’s not ours.
and it’s called a controlled versioning system, it keeps it working and what is submitted and what is under testing etc. etc. under control.