Especially as they've created their own 3D engine (using C++ and OpenGL if I understand correctly).I used an "off the shelf" engine so to speak so I had a party wandering about a 3D landscape within a week of starting work - the next 8 months were used to improve the look, feel, graphics and models etc.
They would have spent many months just getting their engine to display anything let alone a 3D landscape!
They started back in 2001 and they have 25 people in their team so it's fair to say a LOT of work has gone into this.
Good to see there are now two fan-made projects on the go!