Whereas a dynamic library is a single file, a Mac OSX framework is a directory with a specific hierarchy that gives you flexibility in versioning and sharing of common resources.
If I write an RSS parser framework and embed it in an app, when that app is installed it will be put into /Library/Frameworks. If I then open source that framework and somebody else embeds it in their app, it is guaranteed that it will be loaded exactly once. In this respect it is like a dynamic library.
Where it differs however is that multiple versions of that library can live inside the same framework. So if I make substantial improvements to the library, up the version number and embed it, it will continue to live inside that same framework directory and will share the same common resources. OSX recognizes that while these libraries are not the same, they are related.
If you're running on OSX, check out /Library/Frameworks to see what frameworks external applications have installed and how they've organized their resources. Or look in /System/Library/Frameworks for what comes installed by default.
I can't speak to the specific technologies other sites are using but there are enough academic papers out there to allow one to roll their own implementation.