Sure! Both for you adapting it to the German Wikipedia and for me adding DM and Euro it. In fact, adding a new currency is pretty easy, although I think I'll change the structure so that individual currencies are stored in individual pages, for an easier maintenance.

But first tell me: do these numbers take into account the change in currency, so that values in DM get automatically converted to Euros if I simply go multiplying year after year? Or will an input in DM also output in DM? Because I think the best thing is for currencies to not be converted, requiring the user to do a conversion by hand, as it would be quite difficult to keep track of which currency was valid for which year.

Also, could you please provide me a list for Euro-only inflations? If I'm going to add the older DM, it's fair I also add the Euro itself in the same move. -)

And what about Germany before 1951? Is data available?