"lasso" (a bit 0T)

Hey, A prospective client has asked me to try to convert his Swedish site so that visitors have a choice between Swedish and English, which is not a problem as I am fluent in both languages. After going through the site to convert I was just checking out the current pages and I saw that all the links have a .lasso extension instead of the "normal" .htm,.html,.php etc Did a quick search on google and found this http://store.blueworld.com/lp7.lasso sure looks like the same stuff but am not sure... Anybody here worked with Lasso? any suggestions or comments? Thanks, -Ryan