When Apple executives released the new application called Photos in the spring of 2015, they left open a very short window in which iPhoto fans could download and install version 9.6.1 of iPhoto, which is the end of the line for that application. Apple had apparently adopted a rather arrogant policy in which they were compelling iPhoto users to make the transition to Photos and to the iCloud by locking iPhoto users out of using the latest iteration of iPhoto anymore.
How did they accomplish this? In two ways: (1) by making sure that iPhoto before 9.6.1 was not going to launch under the newest Mac OSes; and (2) by removing version 9.6.1, the last update, from the App Store so that it could not be downloaded. It is their game, and you have to play by their rules, they were saying. If you could not manage to download version 9.6.1 while it was still available through the App Store, you were out-of-luck. Too bad for you!
Apple fixed things so that version 9.6 was not going to launch under Yosemite, so many iPhoto fans, who did not check in at the App Store to download the final upgrade before the window abruptly closed, got angry and cursed Apple for leaving them in the lurch. They vented their anger all over the Internet, as they repeatedly encountered what appeared to be an error in the App Store application whenever they tried to download the upgrade to version 9.6.1 of iPhoto. When they tried to download the iPhoto update, all they would get was a cryptic message saying that the file was "temporarily unavailable." This frustration went on for about six months. I was among that group who tried, but failed, to download that final upgrade.
Well, the frustration is over, because today, as always, I clicked on iPhoto listing in the Updates tab of the App Store, and, to my surprise and delight, the upgrade to version 9.6.1 of iPhoto actually began to download! I just installed it on the Yosemite partition of my Mac Pro, and it launched just fine. The "temporary" freeze-out appears to have ended.
Now, all those diehard iPhoto fans—some of whom complained that they were unable to access their treasure trove of images—can get off their knees: their prayers have been answered.
However, these humble supplicants should not overlook the lesson: you never know how long the download window will remain open. So, if you want version 9.6.1 of iPhoto, you better grab it while you still can. You just never know if that window will soon crash right on top of your hands.