@Joey > The CDJ-350's were released before rekordbox had a performance mode, so they never came with a license, thus the need to buy it if you wanted to use it.
Nobody is taking away your paid software - you are welcome and eligible to continue using anything you already own. If you have a rekordbox 5 license, you can keep rekordbox 5. You're not being forced to upgrade your software OR hardware.
Any software you've purchased was to use that version of the software. If you buy Ableton Live 9, you have to pay again for Ableton Live 10 - you don't get it for free. Same with rekordbox 5 to 6, the only difference is we changed to a subscription model to better serve our customers through updates and new features regularly.