No, but you can install any of the available PPC-based Linux distributions that will allow you more flexibility in configuring it as a Samba server. The ones that use KDE as their desktop environment have a configuration section for Samba services that might be easier than configuring the smb.conf file right off the bat.
Check out DistroWatch for the available PPC-based Linux distros out there. Good luck!
• Apple iMac G5 17" (2 GHz G5) - Mac OS X 10.5.8/Ubuntu 10.04
• Asus Eee PC 901 (1.6 GHz Atom N270) - Fedora 13
• Apple Macintosh Quadra 650 (33 MHz MC68040) - Mac OS 8.1
• "JHVH-1" (2 GHz AMD Athlon XP 2400+) - Slackware 13.1