Like OS X, Darling includes MANY third party components. These are typically licensed under APSL, GPLv2, LGPL, BSD and similar licencies.
git clone --recursive https://github.com/darlinghq/darling.git
See the build instructions.
darling-dmg is a component of Darling used for mounting DMG disk images (with an HFS+ filesystem) through FUSE. It can be used standalone, without the rest of Darling, or even as a library in your own project.
For more information, visit the project homepage at GitHub.