Can I reinstall Aperture?
My 27 inch iMac needs to be replaced according to Apple. Can I reinstall Aperture on the new Hard Drive?
iMac, OS X Yosemite (10.10.3), HD is backed up on Time Machine
iMac, OS X Yosemite (10.10.3), HD is backed up on Time Machine
If you restore the system from the Time Machine backup using the Setup Assistant directly when the Mac boots again after you reinstall the system on the new drive, it will also migrate all applications including Aperture. This will be the easiest approach.
Which version of Aperture do you have? Did you buy it originally from the App Store? Then you can reinstall from the App Store, provided you have Mac OS X 10.10.4 installed. Then you can reinstall Aperture 3.6.1 from the Mac App Store Purchases pane.