I do a lot of home brewing but have a binder that I use for my process & notes. I did however find two PPC compatible homebrew software packages.
1. BeerSmith - $25.00
http://www.beeralchemyapp.com/beeralchemy.shtml
2. Brewmeister $15.00
https://www.macupdate.com/app/mac/6263/beermeister
After looking at them, I am impressed with BeerSmith. It looks pretty fantastic. It's try before you buy which is nice. It also looks like there is a tablet iOS version as well which I think is pretty cool.
There were some others I found but they require intel 10.6 or later. Good luck.