The problem is, Epson has not indicated if they made their 10.5 or 10.4 drivers PowerPC compatible.
Apple transitioned to Intel with 10.4.4, but allowed PowerPC owners to use up to 10.5.8.
You should try to select either the 10.5 or 10.4 drivers from Epson, changing the 10.9 pulldown menu on the website. If neither work tell Epson they need to indicate if it is Intel Only on their website.
I noticed the filename is the same for 10.5.8 or later:
Since no PowerPC compatibility exists in 10.6.8 or later, it suggests that driver is only for Intel. Only the 10.4 drivers are different, so you should try them in this file: