We offer Julia at https://cocalc.com both via Jupyter notebooks and Julia’s own Pluto notebooks. That said, Julia tends to be a lot more memory intensive than other language we support, so the free tier is not as useful.
If there is a way to get into a Julia repl, I couldn't figure out how.
No, it does not. When I type "print(1)" into the left box and click "Run" all that happens is that the "Sign up" button wiggles.