Not a clone, Space Miner: Space Ore Bust (on sale for 0.99$) and it's spinoff Space Miner Blast (free with IAP) are the closest things to it, both games are awesome go get them now!
This thing (Dangerous: Null Space) is something that I'm following. According to the devs it's basically a true 4x sim. Much more complex than GoF.
For the mining/fighting aspect of the game, Space Miner is an excellent game. For the trading aspect, Warpgate isn't too bad, but I never enjoyed that game too much.
Any other games? Warpgate looks like the game I want but $4.99 is to much for a old game like that. Ultraviolet sounds very buggy from the reviews.
Try Galactic Phantasy. Not as good as GoF, but it's not bad either. http://itunes.apple.com/us/app/galactic-phantasy/id431504950?mt=8