"Adnan is keen to stay, but he has some influences round him," Moyes said.
"We really think an awful lot of him, he is a Manchester United player and I am sure he will (continue to) be.
"We think this is the best place for producing and giving young players an opportunity. We think we do it better than anybody.
"I do it, maybe not as well as my predecessor, but at Everton we always put young players in the team when we thought the time was right."
"It is part of my remit to promote young players and Adnan has been promoted already. The next part is to become a regular first-team player."
Januzaj's emergence has left £12-million ($23.4-million) signing Wilfried Zaha without a minute of first-team football since the Community Shield, but Moyes insists the former Crystal Palace winger will get his chance.
"Wilf has not appeared, but we have not felt we have had the opportunity," Moyes said. "But I want Wilf to get used to what happens here.
"The competition is hard and it is just impossible to get all these players a game at the one time.
"It is important Wilf gets to see the level of the training here, the level of the players and the quality they have got. But he is getting better, which we are pleased about."
Moyes has also backed Ashley Young and Marouane Fellaini to improve after being criticised following last week's 4-1 defeat at Manchester City.
"Ashley didn't play particularly well against City, but you could probably have picked another half-dozen who didn't," Moyes said. "He will be OK and we will give him every chance to prove what he can do.
"As for Marouane, I think when I took him (from Everton) he looked a little bit short and not as sharp as I wanted him to be. He has found the tempo of the training slightly different and because of that I thought he was a little bit behind."