Dear expert,
I came to US from Poland on June 25, 2009 to work as postdoctoral fellow at public University. Visa status is J-1. I began to get paid since June 30, 2009 and I haven't paid any taxes so far. My question are:
1. Will I be free of taxes till the end of 2010, till the June 25, 2011 or till the June 30,2011?
Since I do not pay taxes in US must I pay them in Poland?

2. If I stay longer than 2 year, I will begin to pay taxes in US. Will I pay retroactively taxes which I did pay for 2 years?
If I must pay unpaid taxes from the first second years does it mean than I will pay double taxes (current + "old")

Please clarify this

Thank you in advance,

Jan