Its a rewrite in that they threw out nearly an entire codebase and built it on top of something different. If tomorrow Microsoft said "lets get rid of Vista and

Its a rewrite in that they threw out nearly an entire codebase and built it on top of something different. If tomorrow Microsoft said "lets get rid of Vista and build something new on top of Ubuntu", I think it would be fair to call that new version of Windows a rewrite despite them not having written the underlying code. Also, lets not forget that a fair amount of work (understatement) went into Mac OS X post NeXT.