From what I've been able to glean from the KeyShot forum and their online Help, if you purchased KeyShot 10 from Luxion with maintenance and it is still active then you can download KS11. If you don't have active maintenance on KS10 and want upgrade to KS11 then subscription pricing is in effect. This is only for KeyShot Pro purchased from Luxion.
I just installed Keyshot 11, and interestingly, it works and shows the Alibre activation when I open it directly. However, if I try to export directly from Alibre, it asks me to activate my license - which doesn't work.