Apple may have been inspired in part by their experience with XGrid [http://www.apple.com/server/macosx/technology/xgrid.html], based on the NeXTSTEP application Zilla [http://www.omnigroup.com/mailman/archive/macosx-talk/2000-Se...], and perhaps by PDO (Portable Distributed Objects) [http://en.wikipedia.org/wiki/NeXTSTEP]. I mention these somewhat obscure influences in response to your grid observation. Obviously there are several other (probably more immediate) influences on GCD and OpenCL as well (LLVM, OpenGL, various academic research on parallelized programming, etc.)