Tax exemption and the double taxation agreement

I would appreciate if any of you finance experts have any thoughts on this problem. Its quite complicated and I even get confused when trying to describe it.

I came here in August 2004 and signed a two year contract for a university research position. I received an income tax exemption for these 2 years under the double taxation agreements (because I was being taxed at home). I only worked one year at this contract and in August 2005 I started a tax free Stipendium funded by the EU which is running until September 2006. From this september I am going to work on a normal university contract BAT IIA.

I guess what I want to know is will I now be taxed for the months between August 2004 and August 2005? Any ideas?

I am not a tax expert. However, I believe Germany taxes based on a full calender year. You become liable for German tax after living six months here. Therefore, you are not liable for taxes from August 2004 to December 2004, but you are liable for the amount paid to you from Jan 2005 to August 2005.