Apple really pissed me off about this. Magsafe is not licensed. Buy Magsafe bricks, cut the end off, and make a battery that can charge MacBooks? See you in court.
Apple hasn't made a similar product in the seven years since this case. That's ridiculous that they would discourage accessories for their product. That's free R&D for them.
http://appleinsider.com/articles/10/11/01/hypermac_to_be_reb...