According to the Gimp-Print web site, Gutenprint 5.2.4, is compatible with OS X 10.3 or higher went into full release July 29, 2009 and it supports drivers for your Epson Color Stylus 860. I recommend installing 5.2.4 rather than the 18 month older and out of date Gutenprint 5.0.2.

After installing the Gutenprint 5.2.4 drivers,
  1. go to System Preferences > Print & Fax
  2. Control+Click on the printer list and select "Reset Printer System"
  3. After that you will have to re-add your Stylus 860 and any other printers you have.
  4. Be sure to select the driver labeled "Epson Stylus Color 680 - CUPS+Gutenprint v.5.2.4". You may have to use the Select a driver to use option to actually get to that driver.

If we knew what it was we were doing, it wouldn't be called research, would it?

— Albert Einstein