TDE - the The Dark Eye rule set - was conceived by a few people who had been translating D&D into German language as well - and did a few other fantasy-related projects, too.
The rules set has gone through quite an evolution - the far biggest break was that towards the the edition, which is used in Drakensang, and which was updated several years ago as the 4.1 edition.
Drakensang uses a slightly modified rules set to make he game more accessible for computers/video gaming.
Right now, only the 4th edition is available in English language (as a book), but it seems to be scarce and difficult to come by. You might have perhaps the best luck with Benelux-based shops, although I've also seen a few rare speciments of the basic rules book on German conventions as well.
Edit : It doesn't seem to be as scarce as I thought :
http://www.amazon.com/Dark-Eye-Basi...4020/ref=sr_1_1?ie=UTF8&qid=1310978329&sr=8-1
Edit : Uk is cheaper, I think :
http://www.amazon.co.uk/Dark-Eye-RPG-Fanpro/dp/1932564020/ref=sr_1_1?ie=UTF8&qid=1310985895&sr=8-1
The greatest drawback is, however, that only very, very few books have been translated into the English language at all.
I fear that the company is just too small to be able to afford it. Someone else would have to do it.
My personl opinion - and this is really my personal opinion - is that that TDE is more foused on hat I call "social interaction" or "social role playing" than (A)D&D.
There are a lot more skills in that direction, as far as I know - but I must admit that I haven't had an (A)D&D rule books in the last years, since they aren't cheap here, and I didn't have much of a willing to buy one so far.
Last, the 4th edition has one point which is eiher hated or loved : Its complexity. The rules set has become very, very complex - and that especially in the areas of a) combat and b) magic.
There are most certainly fans, "number crunchers", who just love this complexity, and defend it wholeheartedly.
A lot of others, however, battle its complexity because they believe that its complexity makes the system unaccessible for the masses (read "masses" with a grain of salt, because "masses" isn't a really great number, since the German market regarding pen & paper RPGs is actually very small, and there are quite a *lot* of different systems competing for an audience !) and especially for newbies.
This is quite imilar to the battle of those who just love the Dark Fantasy aspects of TDE (the "Black Lands", which will soon transform into the "Shadow Lands" with an upcoming descriptions book), which was introduced into the system around 1997/1998/1999, and which is therefore favoured mostly by those who came later to the system and the world of Aventuria, and those of the older generations, who still remember TDE's Fairy Tale aspect and would like to have the "Old Times" back (and not so much Dark Fantasy anyway).