Apple’s announcement verbiage reads:
The Mac OS X Lion Up-To-Date upgrade is available at no additional charge via the Mac App Store to all customers who purchased a qualifying new Mac system from Apple or an Apple Authorized Reseller on or after June 6, 2011. Users must request their Up-To-Date upgrade within 30 days of purchase of their Mac computer. Customers who purchase a qualifying Mac between June 6, 2011 and the date when Lion is available in the Mac App Store will have 30 days from Lion’s official release date to make a request.
Lion is normally priced at US$29, a price that covers all Macs authorized on your iTunes account. Apple has said that Lion will ship in July, but a specific release date has not yet been named.