As far as I can tell, there is no catch, other than they hope you'll produce software for the Windows ecosystem (but there is no penalty if you don't). You'll probably also continue using MS tools afterwards (but this is of course not mandatory either).

As for the requirements, you have to have a company, small enough when entering the program (can outgrow the entry requirements during the three years and still stay in), and it has to produce software (service or packaged).