Lately they have even been challenged, and lost, by another competitor in the political arena: The Pirates, that stand for civil liberties even more then the FDP does.
I would not call the german pirate party a "libertarian" party. Many of them support the idea of an unconditional basic income, which in my opinion is rather socialist.
I don't think that real "libertarian" parties do exist in germany, at least not to the extent described in this thread.