You can't get business ADSL, SDSL or a leased line in Germany I woudl be surprised if that is the case.
In fact knowing Germany I am not surprised that using a consumer line for business is not breaking some rule.
Of course you can get business ADSL, SDSL or a leased line in Germany. It's just a lot more expensive (on the other hand you often get a much better service).
Code is not big, other resources like images, etc, may take more space, but that's often not an issue.
More importantly, 'consumer grade DSL' may be all that's available depending on the location.
Of course, the website is not being served from there.