Thanks to lobotommy's comments I contacted the WBaduk administrator via email. He was very friendly and created an OroBaduk account for me. He also told me that an English client for WBaduk will be developed this year.
I now played my first game and these are my impressions:
The client works fine. I challenged a few asian players and soon I had a game going. In the middle of the game, I misclicked, and there was no button for Undo.
Score estimator and pre-play is available during the game. I did not go to counting, I had to resign before that.
All in all, the device seems to be a little small to play a game of Go. I have a much better overview and can take the game more seriously on a bigger board.