Apple may have been inspired in part by their experience with XGrid [http://www.apple.com/server/macosx/technology/xgrid.html http://www.apple.com/server/macos

Apple may have been inspired in part by their experience with XGrid [http://www.apple.com/server/macosx/technology/xgrid.html http://www.apple.com/server/macosx/technology/xgrid.html], based on the NeXTSTEP application Zilla [http://www.omnigroup.com/mailman/archive/macosx-talk/2000-September/028352.html http://www.omnigroup.com/mailman/archive/macosx-talk/2000-Se...], and perhaps by PDO (Portable Distributed Objects) [http://en.wikipedia.org/wiki/NeXTSTEP 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.)