From the faqs:
"Thank you for your interest in JRiver Media Center. It is scheduled for release soon.
Media Center 9.0 can be purchased from the Help section of the program. The beta version is specially priced at $34.98 until release -- the price at release will be $39.98.
A Media Center version 9.0 license will also work with Media Jukebox version 8.0. An MJ version 8 license purchased by December 3, 2002, will work with MC version 9. MJ Version 8 licenses purchased after December 3, 2002, can be upgraded to MC version 9. The current upgrade price is $12.98. On release the upgrade price will be $19.98.
If you previously purchased MJ version 7.x, that license will NOT work with 9.0. There are no special upgrade prices from versions prior to 8.0."
Hope this helps better.
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Listening to: 'I Can't Give You Anything But Love' from 'Blonde Original Soundtrack' by 'Patrick Williams' on Media Jukebox