I'm sorry to tell you, but WINE will not help you run x86 Windows programs on PPC.
WINE stands for (W)INE (I)s (N)ot an (E)mulator. Instead WINE is a collection of libraries that mimick the Windows API and therefore allow to run Windows programs without actually having Windows installed. Nevertheless, WINE does not translate the machine code of applications to different processor architectures. Since your computer has a PPC processor (G4), and all Windows applications are either x86, x86_64, IA64 or ARM, WINE would not be of any use for you - therefore it's not available on Ubuntu for PPC.
I'd suggest to look for open source alternatives for the Windows programs you'd like to run, or to get an x86 (or x86_64) based computer in order to run Windows applications.
If this is not an option, what you can do to run Windows applications is to set up a virtual machine with an emulated x86 CPU, but be warned, this will be terribly slow (meaning nearly to totally unusable). There are numerous solutions for this, probably qemu is the one best supported under Ubuntu. If you have a Windows licence, you can set up a virtual machine with Windows installed. If not, you can set up an x86 Linux and use WINE in that. I also read, that someone managed to set up a Windows 98 within dosbox, what might eventually be faster and easier to do.