Copyrights have not expired, and will not expire, so long as Congress is free to be bought to extend them again.
The danger in media concentration comes not from the concentration, but instead from the feudalism that this concentration, tied to the change in copyright, produces.
Monopoly controls have been the exception in free societies; they have been the rule in closed societies.
By the time Apple's Macintosh operating system finally falls into the public domain, there will be no machine that could possibly run it. The term of copyright for software is effectively unlimited.
