Apple did not just ripoff Xerox. Apple compensated Xerox $1M for their visits. Apple made substantial extensions on every technology shown during Jobs’s visit especially on graphical interface and pointing devices. Xerox published a reasonable level of their results in the open literature also. Jobs deserves full credit for developing and marketing the Macintosh. Here is an interesting report on Xerox Parc and Apple.
http://www.newyorker.com/reporting/2011/05/16/110516fa_fact_gladwell?currentPage=1
Better than that. They gave them a million dollars worth of pre-IPO Apple stock, then valued at $7 a share. That stake, if Xerox had held onto it, would be worth billions today.