Folder name
Hey, I had the exact same problem. After I read this threat and people said to install it "right" I checked out where I put it in my application folder.
To be more organized, I created subfolders in my Applications Folder.
I.e. System Progz, Tools, Graphic Progz etc. So that they are all at the beginning of the list I added in front of them to make it " System Progz". When I installed smcFanControl into that folder it would always prompt for the password, but once I placed it in a subfolder without the it worked.
Maybe that will help others with the same problem.