WBO

The board is updated in real-time for all connected users, and its state is always persisted. It can be used for many different purposes, including art, entertainment, design, and teaching.

WBO lets you create public and private boards:

• The public board is accessible to everyone. It is a happily disorganized mess where you can meet with anonymous strangers and draw together. Everything there is ephemeral.
• You can create a private board with a random name, that will be accessible only by its link. Use this if you want to share private information.
• You can also create a named private board, with a custom URL, that will be accessible to all those who know its name.

WBO is a completely free and open-source project. See on GitHub.