Panther: MacOS X update most likely not free

“iDisk, .Mac’s online storage service, is faster and more convenient when you use it with Mac OS X v10.3 Panther. Thanks to an entirely new architecture for accessing iDisk, .Mac members who upgrade to Mac OS X Panther* will get incredible performance and the ultimate convenience of offline access and automatic synchronization between the desktop and the Internet.”
My interpretation of this would be that Panther will not be a free update.