MixVibes provides for all users the abilty to save the licensekey in the user profile.
This is refered to in several places while getting the initial software installed.
An open license key would not make any sense as this would mean the manufacturer can bundle the software to unlimited number of controllers.
Also other features may depend on license key, like upgrade discounts used to. And if the controller is resold the license key of the LE is no longer valid as it has become a Cross or Cross Pro partial payment.
The Free version has no license. However does not support MIDI.
You could try sending an email to
support@mixvibes.com with your info and the proof of purchase. Though this is rarely approved.