Well, another way to make this work better is to create two downloads and a two step operation. Have the linkbucks link go to an index type page with the download link (also a linkbucks url) and have that destination be a paid download program like sharecash. The index page will also promote a second, related free download if the user completes an offer.
This way the total hoops a person has to go through is just clicking through two links, then downloading---after that, he may backtrack and go for the second download via CPA. But it will only feel like they've done two things (click to the site, click to the download). If the first page had CPM ads on it, you've basically gotten paid four times (2 paid linkbucks links, CPM, paid download) before you've even got to the CPA part. Depending on the traffic funnel and how many minisites/autoblogs are set up, it can quickly add up.