No login is needed to use MindMup. Student/Teacher creates the mind map and chooses to save it in their Google Drive account. When opening the mind map back up from their Google Drive account, you will open it in Google Drive Viewer. You will be prompted to open the map with MindMup - Free Mind Map Web Site.
Student can use this to brainstorm ideas and plan out their writing. Teacher can use this on the SmartBoards with the whole class during lessons, writing and brainstorming activities.