JDownloader is an open source download manager, primarily aimed at downloading from captcha-protected download sites (RapidShare, Megaupload, Hotfile, Netload…) but supporting also any “normal” download (like a picture from photobucket, or actually any file from any server).
Although claiming to be open source (and actually, it’s currently under the GNU GPL), parts of it are close source. Notably because they rely on an undisclosed encryption algorithm for their encrypted links list files. I’ve never understood the point of making those lists undecipherable, particularly since anyone is able to open such a list with JDowloader and to grab the files. Only they won’t be able to easily get the location of those files.
Anyway, there are several easy ways to find the links inside a DLC:

1. The always-working method: JDownloader will never be able to prevent you from using this method, as this would require the complicity of hosters. Basically, this method involves to simply spy your own connection and record what URLs are retrieved by JDownloader. When you load a DLC links list, JDownloader will check if the files are online. With any packet sniffer you can list those links. A more detailed short video tutorial was posted on sala source. Just in case this goes offline (as other DLC decrypters have), I mirrored their video on Megaupload there (tip: if you want to save download wait time, don’t download it yet but rather watch it live on megavideo) and their toolkit too.
2. The easier method, but probably not working with recent DLC files (JDownloader tend to change their encryption method regularly to avoid decrypters): a decrypter made by Seba. It was originally posted on a BlogSpot blog but eventually disappeared. But thanks to FilesTube I still managed to find it and I uploaded it here. It was created around May 2009, so it should work with DLC files created before this date, and possibly during some time after. I didn’t test it with current DLC files.

For a short summary:

• DLC Decrypter version 0.7 (May 2009) by Seba
• Video tutorial that (normally should) always works, and the tools that go with it