The site doesn’t really let you download anything, it says so on the bottom (in German). Apparently it’s mainly meant as an ‘information database’ in other words, they’re just making money from the advertisments. It does appear to download something but those are just website elements (what also happens when viewing a normal website, only usually you don’t get to see a ‘loading’ bar).
I’m indeed getting more and more convinced to just order the sheet music and see/try what it looks like… 🙂