Cool. This is quite usable and seems really handy—it's really fast compared to some heavier online repls. (definitely a use case for me)
How is it set up? I was definitely able to crash an instance I was in as well as read from root, but seemed all it took was a reload of the page and it snapped right back in without any real startup wait.
*edit: I just saw that you posted the source code as well. I'll definitely be exploring!
This seems not cheap to operate. What is the business model?