From what I understand, no. The map editor for this mod requires each user to buy his own license, so unless you buy yourself(some guys in the community will surely) you can't create maps.
I'm not sure if this will necessarily be the case. Look the Unity Pro vs Unity Free features--when it comes to straight coding or scene creation the two are largely the same.
However, Unity Free doesn't come with LOD -- Level of Detail -- native support, which is rather important when it comes to large and detailed scenes. Maybe FSE could find a way to script around this. (Come to think of it, I have no idea how LOD will work with destructible props, but I'm sure Vince and co will figure a good system out.) Only time will tell