I currently mine with my own HDL code -- which is not performing very well yet (!). I have deliberately not looked at or downloaded fpgaminer's code in order to avoid being the target of accusations.
The legal definition of 'clean room software' is much more flexible than most people assume.
You can look at fpgaminer's (or any other available) design.
You can write detailed specifications based on the design while looking at it. You have to be careful not to include any copyrighted material in the specification (IE code snippets.)
The same person can use the specifications to develop a new design.
The only limitation is: you cannot reference the original code while developing the new code.
For everyone else, the LX150 isn't supported by the free version of the Xilinx tools. You'll have to buy the full version ($5K?) to develop for this board.