Get newer software. Or buy an old Mac. Better yet, provide more details so we can figure out what you are trying to accomplish. Such as... what Mac do you have? What version OS X? What software is this? And so on...
Not going to happen. That's a PPC app which requires "Rosetta" to run on an Intel Mac. The last version of OS X that you can install Rosetta to is Snow Leopard 10.6.8. You may be able to find another way by using an emulator such as "SheepShaver". If you try this, you're on your own.
Chscag's response is correct, however there may be an alternative. There is a Windows version of that same game available, and it's possible this will run under WINE. WINE is a piece of software that basically tricks Windows software into thinking it's running in Windows. Sometimes this works and works very well. Sometimes not entirely well. And sometimes not at all. When it does work well, performance is about as good as if you were running the app in Windows because you don't have to emulate the hardware, unlike SheepShaver where the emulator has to emulate the PPC hardware. Of course if you don't have the Windows version, you'd have to determine if buying it, then attempting to get it to run under WINE is worth the effort and $$$.
There are a few different pieces of software for OS X that utilize WINE. CrossOver is probably the easiest to use, but isn't free. It does have a free trial though. If you know what you are doing, you can try Wineskin. This is my personal favorite because it wraps up Windows apps in a nice, tidy little package that looks just like any other app for OS X. And it's free!