Using the links above you can download a compressed stable or beta release.
To use, you should extract the file and move the org and com folders into the main src directory of your project. Alternative, you can place the org and com folders elsewhere, and manually set up your source path in your project settings to point at that folder. Using the first method is safe, as it keeps the code bundled with your project, which means it easier to distribute and keep track of, and any changes you make to one project will be isolated from your other projects. The second method allows you to share the same set of Axel files between projects, but is more advanced as it ties your projects together.
Axel is completely open source, released under the MIT License (click here to view). This means that you can use it in your free or commercial projects, without needing to give attribution. The only restriction is that when distributing any source for your projects (if you choose to do so), you must include the Axel license file that comes with the library.