If copy protection is the only issue, as a registered purchaser, they would be able to send you new versions with the copy protection at zero cost to themselves (other than the pen drive). I guess you would have to return the protected SD90 pen drive (or you would now have two copies of the style for the price of one!), so even that shouldn’t be a big deal.
I understand that Ketron would probably like to add some Real Guitar and Bass tracks to them, and that would definitely justify an additional charge, but if the customer simply wants to use the old SD90 style as is, I think he deserves to have the copy protection changed for next to nothing.
I sincerely hope Ketron do the right thing for their loyal customers.
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An arranger is just a tool. What matters is what you build with it..!