I'm not sure how the GPL covers a particular packaging configuration of a build of something which has GPL'd source. Sure the source can be redistributed, but the binary possibly not. In practice, this is not much of a distinction because you can build the package from the source, but in this case the source probably doesn't have anything in it saying "Apple has built this source code into OSX." What Apple has done is essentially building a binary of MacRuby and installing in a location on the filesystem of a MacOSX Lion install. None of which you could claim that the GPL allows you to by-pass an NDA over.
MacRuby is under the Ruby License. I am not sure it prohibits distributions of binaries without source. If, however, Apple decided to include the latest and greatest version of, say, bash, they would be required to give you redistribution rights along with the source. You could, then, redistribute it (thus giving informations about the next OSX) without violating the NDA.
If Apple forbids you to get the source of their GPL'ed parts and passing this source on to others, they are in violation of the GPL and their own right to distribute it is voided.
Apparently you didn't read what I wrote. Apple cannot prevent you form getting the source code, but the source code does not include information like "the binary will be installed to this location and will be considered a Mac OSX private framework." When something is considered a 'private framework' in OSX it's primarily an install location which does not change the source code as install location is usually a build-time option. Build-time options are not something that is covered by the GPL.
