From Axel Project official site :
Axel tries to accelerate HTTP/FTP downloading process by using multiple connections for one file. It can use multiple mirrors for a download. Axel has no dependencies and is lightweight, so it might be useful as a wget clone on byte-critical systems.
I found a working compiled version of axel download manager for my dm800.
You can download it from here : Click here to download axel mipsel
First decompress the zip file then put it in /usr/bin folder of your dreambox and make it executable and enjoy 🙂