ed2k Helper is a simple application that handle ed2k:// protocol in URL from your brother. Traditionally, on Mac OS, those URL are simply ignored because there is no real eDonkey client application. But since Mac OS X, we can run many more application, coming from unix world. So Mac OS can run daemons like mldonkey to use e-donkey network.
Those daemons usually offer a web interface to handle downlaods, searches etc... ed2k Helper will use this web interface to add your files to the downlaod queue.
Simply put the application into your Applications folder, and it should work.
If you want to change default server address or protocol, just launch it.
ATTENTION !! : With Safari, you can not handle urls like e-donkey ones directly. So you will have to drag your link from the page to the url bar, that's all.