Registration: Can I give moderation rights to participants without a JLU account?

Yes, click on the burger menu (three dots on top of each other) of the respective room in the Webconf interface (Greenlight) and select "Room settings". Here you can create a moderator code with which participants are upgraded to moderator when they enter the room. This allows them to start a room without the room creators or other moderators with a JLU account having to be present.