The current version of PDFSlide can be Downloaded Here!
It seems that someone is trying to sell a version of PDFSlide, and it seems to be a version without any major changes. In one case PDFSlide is being sold on a platform that is incompatible with software distributed under a GPL license. I created PDFSlide with the intention of it being Free and Open Source, so selling this software goes against the philosophy under which PDFSlide was created.
Download PDFSlide for free from this website, and save your money for a rainy day. If you want to spend some money consider donating to a worthy charity. Here are a few suggestions:
Information and links concerning the development of PDFSlide can be found on the Development Information page.
Some amazing screenshots of PDFSlide can be found here