No, users do not need to sign in / register to post to a Kudoboard. If you'd prefer not to create an account and stay anonymous you're welcome to choose "Skip Email" and add as a guest.
The only exception is when users are posting to boards created through Business & Enterprise plans; in this case, they are required by default to register before posting.
To post using the Skip Email option:
1. Open the board.
2. Click + Add to Board.
3. Create your post by adding text and/or media and then click Skip Email.
4. Enter the name you'd like to sign the post with, then click Post.