It is, but blockland on mac was origonally just for the intel processors, but then it was updated to work on all macs. I bet either the old version is what works, or it only works right on intel. I have used a g4 proccesor mac that was higher end, and slate storm looked like white water with falling white boxes.
Also, it may take a bit for me to finish the map since I can barely get on my comp this week, I'm gone this weekend, and next week is finals. Also, my map is not just a slate edit, it may change how slate maps are made.