Apple has released the source code for Snow Leopard's new Grand Central Dispatch under an Apache-style license. Grand Central Dispatch lets programmers easily take advantage of modern multi-core hardware. The Apache licensing means it can be safely used in projects wishing to keep the rest of their code proprietary. This is great news for folks writing code that needs lots of horsepower and needs to run on multiple platforms.
Grand Central Dispatch code at Mac OS Forge
MacResearch article discussing the release
Apple's Grand Central Dispatch Technology Briefing
Introducing Blocks and Grand Central Dispatch (Must be a registered Apple Developer to access this article)
Technical Note For Windows Programmers: Grand Central Dispatch uses a technology known as Blocks. Blocks require a language extension to C or C++ known as Lambdas. This language extension has been added to the publicly available GCC compiler and has been submitted for inclusion for the next version of the C programming language. But I don't think it's part of Microsoft's Visual Studio development environment. The proposed extension differs syntactically from Microsoft's Lambda extension. Bottom line, if you want to use Grand Central Dispatch on Windows, you'll want to use the GCC compiler.