Can't enslave professors, so its part of the deal. Been happening about 1000 years. And I'm not sure I care to make Universities into profit centers (any more than they are).
Also afaik John Martinis maintained a paid and tenured position at UCSB during his work at Google.
Its the idea that the University would 'own' part of a commercial enterprise that's chilling. Means even more commercialization of Universities than at present.
Obviously noone should be forced to stay where they don't want to be or prevented to work where they want but in this case it's about what they take and bring with them beyond their innate skills.