Source?
There won't be any kind of source that isnt horseshit.
If the response was "publish this and we will credibly kill you" then I'm not going to blame Assange for burying it. I'm going to blame whatever country he was in for the fundamental problem of not being able to protect people on its soil from Russian assassination.
Assange was told he would be falling out a window if he published it. Then he buried it.
He is only about publishing leaks about western countries that don’t directly tell him they will murder him.
That isn’t a free society.