It is a strategy 4x-game, it was not built on the engine used for Civ V. From what I've read, it actually was based on the Fantasy Wars/Elven Legacy.
I can see the similarities looks-wise myself, but I can also remember playing hexagon board games 30 years ago, it does not mean the Civ 5 uses their engine.
It has nothing to do with the Engine of Civ 5, though I believe the company did admit that they felt they need to make a call to Firaxis and have a conversation to make sure it wouldn't be a problem. It's out, so obviously it wasn't. 4x-hexagon based games are going to look like that, it is just that simple.
Kind of surprising how many people are confusing this. Different companies completely.
Whether the engine is exactly the same or not, they appear virtually identical. From the units not stacking, the way cities defend themselves, the way units can convert to their own water transport, etc. Even the graphics for the terrain are virtually identical. There is no confusion....aside from a few minor changes in the games economy, this is basically a civ 5 mod.