I've been working on this the past several nights and just wanted to
provide some progress info.
I'm using the Debian "squeeze" (testing) distribution because it has
support for the armel processor that the Seagate DockStar has. Debian
installation notes on http://peterwong.net/blog/?p=115
The netatalk package (2.1.2) "worked" right after installation. I did
have to enable the atalkd service in the netatalk configuration. Using
Marsha's modified AppleShare CDEV in an Apple IIgs allowed me to mount
the share using cleartext authentication. Randnum authentication (if
you're concerned about plaintext passwords going through your network)
is not supported because the randnum UAM is not built in the netatalk
package.