Understanding Gorman Polar Form
After doing some reading on the topic, it appears we would estimate this equation as we would with any other demand estimation. 

the reason why the term $b(p)m$ is written this way is due to the assumption of homothetic preferences (or homogeneous of degree 1, this dosen't matter in demand analysis). Since Gorman polar form is a homothetic form this implies that:

$$v(p,m)=a_i(p)+b(p)m \equiv a_i(p)+b(p,m)$$ 

more specifically $$b(p,m) \Rightarrow b(p)m$$ 

if preferences are homothetic or homogeneous of degree 1.