If I have income only through freelancing (developing software for a US based Company) and am not a incorporated business do I need to file ITR4 or ITR2
ITR1 or ITR2 needs to be filed. Declare the income through freelancing in the section "income from other sources"
Since you are living in India and earning income not from salary, you must file your tax return under ITR4(Profits or Gains of Business or Profession). You can do it online on IncomeTax India eFiling website, step by step guide available here.