If it was neatly designed, developed freely and sported a neat GNU license, with all the same features as early Instagram (none of the bullshit, no stories and all that).
An app and a website would be available.
Would you create an account? If you already do have an Instagram account, would you move to the new FOSS platform? Would you try to get your friends to move, too?
e: before I'm pointed to /f/freeasinfreedom, the question is meant for a broader audience than Free Software enthusiasts