You can use screenshots / images of the Scratch application and website in a book or presentation, and consider them to be licensed under the Creative Commons Attribution-ShareAlike license. We ask that you include a note somewhere in your materials saying: "Scratch is a project of the Scratch Foundation, in collaboration with the Lifelong Kindergarten Group at the MIT Media Lab. It is available for free at https://scratch.mit.edu".
The Scratch Logo, Scratch Cat, Gobo, Pico, Nano, Giga, and Tera are Scratch trademarks, and can not be used without explicit permission from the Scratch Team.