I think Radek is asking a different question (emphasis mine):
Radek wrote:I want to ask you: do you now any discuss group in internet in ancient greek language (attic or koine)
Here on Textkit the Agora
is for conversation in Latin and Greek. There has been more Latin than Greek discussion, but we've had a few smaller conversations in Attic.
There is a Yahoo group called Graece
which is email list. I was a member for a while, but traffic is very, very light. Some months go by with nothing.
That's all I know of.