Forcing/Getting app to run on lower Mac OSX version I bought some software; on the back of the cover it says the minimum version that it supports is 10.4.11 which is the same as my Mac. However, after copying it to the Applications folder, it says it can't run on this version of OS X (I have checked in About this Mac, and the version matches what's on the CD cover).

I right clicked the app, Show Package Contents and opened its info.plist; there it said the minimum version supported is 10.5, so I changed this to 10.4.11, saved the file and tried opening the app, but it still wouldn't open. The message box looks like it's from the OS rather than the application, so the app hasn't even started before I get told I can't open it. 

Is there a way to trick it into allowing it to open, and hopefully nothing will go wrong, seeing as according to the box it can run on my Mac.
NSBundle and CFBundle aggressively cache the contents of application bundles to improve performance. Although you edited the Info.plist, the Finder and Launch Services don't yet know that the application is any different.

Running the following command in Terminal to touch the application bundle will force the Finder (and Launch Services) to re-register the application, thereby noticing the changes you made to the Info.plist:

touch "/Applications/My Cool App.app"


After running that, deselect the application, then reselect it in the Finder, and then try launching it.

Note that this won't necessarily guarantee that you'll be able to launch the app. The developer would need to make sure they set a deployment target of 10.4 and/or use weak framework linking to assure that the app will be fully backward-compatible.