The project comes with license information… "including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
-Free for use in any UE4 project-
Anyone is free to copy, modify, publish, use, or compile software,
either in source code form or as a compiled binary, for use in any
Unreal Engine 4 game, simulation, arch-viz, or other related UE4 projects,
both commercial or non-commercial."
I think you are in the clear for commercial.