You can directly download- you don't have to use their downloader.
See the Gog downloader mode- notice how mine is off? If you click with it off, it downloads directly. I don't think it supports other speed up programs (especially those that download over multiple threads), but you can download directly.
-wraith808
Well, yes and no. If you live on the other side of the pond or have really high speed internet service it isn't a problem. But where I'm at, out in the middle of nowhere with satellite internet, I keep getting dropped packets and timeouts. When you start the download you only have so many minutes (10 I think) before the URL ceases to work. Then you have to re-start your download with a new URL. This is to prevent people from sharing the download URL with their buddies. Because of threshold limitations, the only time I can download without using up my limit is between midnight and 6 AM when it don't cost me, so I can't just sit around renewing the URL every time the download stops for more than 10 minutes. If I don't get my beauty sleep I can get quite ugly.