A court convicted nine Muslims on Friday of belonging to a terrorist group because they incited hatred for non-Muslims.
Bouyeri, who already has been sentenced to life in prison for the Nov. 2, 2004, murder of Van Gogh, was found to be a leader of the group, but the judges said he could not be punished further.
The group's goal was "stirring up, and or inciting hatred, and or threatening" non-Muslims, the judges said.
"Who sows hate lays the basis for crimes that can cause grave fear," Judge Rene Elkebout said, reading the ruling. Such crimes "strike at the heart of the democratic order," he said.
The heaviest sentences were given to Jason Walters — who has an American father — and Ismael Aknikh, who were found guilty of attempted murder when they threw a hand grenade that wounded five police officers on Nov. 10, 2004. Walters received 15 years in prison and Aknikh received 13.
The other members were given sentences ranging from one to five years.