Even though that's for PS2/Xbox, I'm assuming it applys to the PS3/360 in similar ways.
Basically, you (probably) CAN mod the PS3/360, BUT it is illegal. And due to copyright/piracy issues (as said in the quote), no one will make the mods, or if someone does, it WILL be nearly impossible to find.
Yes, and what I said? [/sarcasm]