Aperture 3.6 was one of the final versions of the software before Apple announced that Aperture, along with iPhoto, would be discontinued and replaced by Photos, a new application that integrated features from both.
Have an old Aperture library you’re trying to resurrect? There are still migration scripts and passionate ex‑Aperture users in forums like ApertureExpert — the community endures even if the app doesn’t. Apple Aperture 3.6 -ked-.dmg