It is free, you should read correct:

"Attention: We offer this safety camera database free of charge to all Google Earth users (please ignore the line "Downloading the plug-in is a chargeable item."). The only thing to do is register at SCDB.info one-time. Now you could download the current up-to-data speed camera database for whole Europe."

Try it, and you will see that you must not pay for it.