So, up until recent I used the Windows version of the first game. However, I recently acquired an Imac G3 PowerPC and I would love to install the mac version on it.

My Mac has Mac OS X on it. Is there any way to install it?

Short answer: No.

Longer answer: the original Mac version is very old and written for the classic Mac OS. Mac OS has only a similar name to (Mac) OS X, everything else is completely different, in fact OS X is actually the successor to NeXTSTEP, so a program written for Mac OS won't run on OS X.

The "Mac" version sold here on GOG is actually the Windows version wrapped up in Wineskin to run without Windows, but Wine only works on intel processors. You only chance of getting the game to run on a PowerPC Mac is to track down a copy of the original Mac version and a copy of the classic Mac OS and hope your hardware isn't too new. You could also try a Mac OS emulator like SheepShaver, but I don't know how performance will be, i never tried using SheepShaver.
http://sheepshaver.cebix.net