Actually, while the program installed and opened successfully, it didn't actually work when I tried to save a couple of image files to a pdf file (specifically, pnm to pdf). It did work with scanning images, but saving into pdf failed. It just seemed to stall, and never make the conversion (I could cancel the job, so it didn't freeze).
I found a file on slackfind.net, which was gscan2pdf-1.0.0-i686-1jsc.txz, and this is working for me. So gscan2pdf can work. But it seems only version 1.0.0.
Anyway, my apologies for initially reporting that the version 1.0.4 package that you did was fully working.