There is now an Octane integration in Unity with a free option (1 GPU) - so you can now use Unity to actually render anything you want with Octane for free
I don’t think there is any problem using the Unity Octane stuff for commercial work as you are definitely allowed to use the free version of Unity for commercial work (You are not allowed to use the free version of Unity “if your company currently makes more than $100k in annual gross revenues or has raised funds in excess of $100k”…)