Hi Flyboy,
X-Plane 10 does not support PowerPC-based Macs, or versions of OS X prior to 10.6.8.
"The bottom line: X-Plane 10 Global is 100% compatible with Macs. You’ll need an Intel Mac (any Mac made since August 2006) and OS X version 10.5 or later"
Since I am not too familiar with Macs, I can give some suggestions
Are you able to update your OS to a "recent" version?
As for your question, ALWAYS check the requirements before buying a game. Based on what the requirements say, I believe there is not an "alternative" solution.
But then again I make mistakes
I hardly doubt this will help you but someone from Laminar will respond to you by the next day so keep checking back here.
-Rishi