Or, from Mac App Store: Frequently Asked Questions (FAQ):

Quote:
If I have already downloaded an app from the Mac App Store, can I redownload it for free?

Yes. You can redownload apps from the Mac App Store as long as the app remains available. You may be asked to enter the Apple ID and password you initially used to download the app.


dkmarsh—member, FineTunedMac Co-op Board of Directors