When you upgrade OS X, or when you migrate your content to a new Mac, software that's known to be incompatible with the new version of OS X is set aside and won’t run on your updated system.
During the upgrade or migration process, OS X creates an Incompatible Software folder at the top level startup drive of your Mac. Software known to be incompatible with the new version of OS X is placed in this folder. You can look in this folder to see the applications that were set aside.
If you want to use one of these incompatible apps, you need to get an updated version that's compatible with your new OS. Apps in the Mac App Store list their compatibility and system requirements on their product pages. You can also check with the app developer to find out if they have a new, compatible version or plan to release one.
Note: PowerPC applications won't run on OS X Mavericks and later.