Undoubtedly it is mostly a donation, the monetary value of their shareholding will be very small and unlikely to ever give them a return.
However, it's no different in that sense from the shares bought in share issues for the company which operates Rangers football club. Mostly donations from fans, who'll never see their money again.
Only difference is that Aberdeen are now on an extremely sound footing both on and off the park, while your team lurches from disaster to disaster. So i can see why the Dons doing well is horrible for you.