You can execute another program on PPC the same way you do it on a PC. CreateProcess() win32 api is one way. Remember, PPC does NOT have a command prompt, so system() is not available (as I recall). There is also no such concept as current working directory or change directory. There are directories on PPC, but there is no way to change the current working directory of the program.
Also be careful where you put files. If you have to cold boot the ppc device the file system gets reinitialized to the manufacturer's default. Files stored on extra memory device are unaffected by cold boot.