Hactar can play both go and capture go. Capture go is easier game for the computer, so Hactar can play it against you without a server.
Hactar plays go using a server, this way Hactar has decent strength in go (Note: Hactar Lite plays at beginner level.)
You can find more information from <a href="http://gowrite.net/hactar/client.php?lang=en">Hactar home pages</a>.