Epic games and Square Enix signed a licensing agreement, allowing Square Enix to use Unreal Engine 4 to develop multiple games over the next few years.
This makes Square Enix the first official licensee of Unreal Engine 4. The agreement also gives Square Enix access to Unreal Engine 3 as well.
Accordingly, Square Enix is now able to develop games using Unreal Engine 3, 4 or their own proprietary Lumious Studio engine technology.
A few months ago, Epic Games announced that their own Fortnite game will be the first Unreal Engine 4-based title in market.