"The Santa Claus traditions, originating from the Dutch folk tales, seem to be true." or
"The Santa Claus traditions, which originated from the Dutch folk tales, seem to be true."
These sentences are non-defining. I'm not sure if any Santa Claus traditions originated from elsewhere though.
I don't think traditions themselves can be true or false. The beliefs associated with the tradition can be. But there are other aspects of a tradition, such as rituals and fictional stories.
It's a tradition that Santa Claus delivers toys to children all over the world from a sleigh pulled by flying reindeer. So, I guess you want a defining, restrictive clause.
"The Santa Claus traditions which originated from the Dutch folk tales seem to be true. The beliefs associated with other Santa Claus traditions are blatantly false."