There will be some sort of fee for the interviewing tools (question templates, interview invite emails, etc).
I'm hoping the tech screen income covers the costs of the site so I can make the applications for online tutoring and possibly classroom demonstrations free. The reason I made coderang was to help me teach my little sister how to code over the Internet without making her set up a dev environment (she's 12), so the potential educational applications are something I really care about.
JSRepl is super cool, I can't believe people are just now starting to use it in their own projects.