Dave de Vos
According to this
recent post by Peter Goldsbury, kyudansha means those with kyu grade or dan rank.
As an aside kyudansha is rarely used. Yudansha is very common. At the Kodokan in Tokyo I think the changing rooms are classified as kodansha 高段者 high dan grade holders, yudansha 有段者 dan grade holders and ippan 一般 ordinary - as a Japanese friend of mine used to say, ippan people. Women have just one changing room.