Well the line is law: infringing copyrights and patents. And the US law is very specific about ideas not being copyrightable, so clones are usually safe.
Serves more as a reminder to the youngsters out there that potential future hirers will use things like this to inform hiring decisions. Legal or not, your history follows you around (I’m old enough to be lucky to not have the stupid stuff I did early in my career available online). Be free, go build stuff for fun but keep clear of your employers space.