You own the plastic and the metal of the console, and can do anything you want with it. You do not own the system software on the machine. This means no reverse engineering the system software, no editing the software, no reselling or redistribution of the software. This includes editing the software to circumvent encryption or DRM on any medium you play on the console, or editing it in any way to use the system software as a gateway to installing another OS or apps. The Other OS hack that is currently out now is in direct violation of the user's licensing agreement.
You can turn your PS3 into a doorstop, or you can run any OS or apps you want on it, AS LONG AS YOU DO NOT MESS WITH THE INCLUDED SYSTEM SOFTWARE. If you can code an entirely new system software to run the PS3 WITHOUT using any preexisting code from the system software included with the PS3, you are welcome to do so, and I encourage someone with the skills to do so to attempt this.
If you have ever pressed "Accept" while updating your system software, then you have agreed to play by Sony's rules, which is just fine for me and the other 95% of the people using the PS3 to play games and watch movies.