Apple opens Grand Central; challenges impede Linux adoption
Apple has opened the source code of Grand Central Dispatch, a sophisticated concurrency framework for OS X. Although this move opens the door for eventually bringing GCD to other platforms, there are still a number of licensing and technical issues that will impede efforts to adopt it on the Linux operating system.
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Although GCD is now open for widespread adoption, there are technical and licensing barriers that could prevent it from being used pervasively on alternate platforms. The high-level GCD API makes extensive use of blocks, a C language extension developed by Apple. This feature has not yet been accepted into the upstream GNU Compiler Collection (GCC) mainline, which means that it can't be used on Linux.
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The blocks implementation is under the MIT license, which is GPL-compatible. This means that there aren't any licensing impediments preventing it from coming to upstream GCC. The libdispatch code, however, is distributed under the Apache license, which is unfortunately not compatible with GPLv2 for a handful of truly inane and exasperating reasons. This compatibility issue was resolved in version 3 of the GPL.
from: Ars Technica
From what I've seen GCD looks like a good piece of technology that I'd certainly like to play around with. If it eventually comes to Linux, that'd be great because it means I might actually get to use it on something I work on.