Should I make open source a website’s API?

I'm a computer science student, you know how important is to showcase your portfolio (ejem… github/lab) to potential employers. I created a website (its purpose is to reproduce educational videos) than sooner or later will allow people to register (without any sensible data). My website's source code is open source and collaborator-friendly, but I have kept the API closed source because of security concerns.

It would be nice to make it open source, and show off all of my peers and personal work invested in this API, but would it be advisable?