I made a Scratch 0.1 mod with first-class procedures, lists and continuations. I forgot about it for a while, but now I've fixed it up and released it on GitHub. 'GrumpyCat's the nickname because it's based on a grumpy old Scratch
Ah, then thank you for the compliment of using our ideas.
You should look up call with current continuation in the Scheme manual for a discussion of all the ways it can go wrong! Some of them won't apply in Scratch, e.g., what happens if you have a file open and partly read, and then return to the place where you're just about to open the file. But some of them are just about the code itself rather than external issues like files.