From what I've been able to find, up until this point there have been only 2 versions known of the Gospel of Barnabas, and both have been dated to the 14th or 15th centuries, pretty much considered to be non-authentic...redacted and harmonized versions of the canonical gospels, with Islamic theology inserted by the author(s).
It's pure propaganda to further brainwash their own people.
Well, that is how the game is played.
“Live a good life. If there are gods and they are just, then they will not care how devout you have been, but will welcome you based on the virtues you have lived by. If there are gods, but unjust, then you should not want to worship them. If there are no gods, then you will be gone, but will have lived a noble life that will live on in the memories of your loved ones.”