Retro City Rampage : maybe deleted in few months ?

Hey !

As you surely know, Retro City Rampage is a great retro game in which you play as "Player", who traveled through time and have to get back in his era. He met a crazy doctor (like the one in "Back in the Future") who need special components to create an engine able to do it. In this game there are TONS of Easter Eggs ! I saw the green Mario tube, the dog from the old game in which you had to shoot ducks and if you failed there was a dog saying you suck (I forgot the name of the game) etc...
And that's why I said "maybe deleted in few months". Because it's not only Easter Eggs, sometimes the developer of RCR (Brian Provinciano) use characters from movies or games in his own game.
The problem is not that I don't like it, actually I love it cause it's a funny game, but did Brian paid the rights to use these characters, scenarios etc... ? It would be EXTREMELY costly to pay for dozens of movies and games's rights, especially for a little indie developer...
What's your opinion ?