> What makes software different from any other labor, intellectual property, or physical property?

Nothing, and that's the whole point! If I buy a house, I can repaint it, tear down a wall or do whatever I please (as long as I stay within the boundaries of the law).

If I buy a painting I can move it, hang it upside down, improve the mysterious smile by adding a moustache with a magic marker or make whatever changes to it that I see fit.

If I buy a record, I can sample it, mix it however I please, listen to it backwards so I can listen to the subliminal ALL HAIL SATAN message it hides.

However, if I buy a piece of proprietary software I can do... nothing, except tick or untick some boxes in the settings menu that the developer bothered to put there.