Earlier today, we noted Apple had recently removed older versions of OS X and other discontinued software from the Purchased tab of the Mac App Store for users who had previously purchased or downloaded them. The apps, which included Aperture, iPhoto, OS X Lion, OS X Mountain Lion and OS X Mavericks, have now returned to the Purchased tab.
The disappearance of the ability to re-download older software irked users, with some calling the action "user hostile." It's unclear if Apple pulled the software intentionally or whether the Mac App Store experienced a temporary bug in advance of the availability of OS X El Capitan. However, the software was unavailable for several days before returning tonight.
Only one of the apps, Aperture, will continue to be compatible with OS X El Capitan.