DarcyRipper.com - How to make money ?

Hey guys,
I've got darcyripper.com, is a free website downloader tool - maybe some of you already used it at some point in time to ripp some themes or related. I don't want to charge for it use but to keep it going I am interested in a method how to make some $$ from it?
It has around 2000 Downloads per month.

Any idea will be awesome! Thanks

make membership something like speed of download
people who pay can download faster