jmc

If the side lengths are 8, 15, and 17, then we have a right triangle on our hands. That means the area is simply $A=\frac{1}{2}\cdot 8\cdot 15=60.$ Now, we find the semi-perimeter $s=\frac{8+15+17}{2}=20.$

Plugging into $A=rs$ and solving for inradius $r,$ we have $60=20r,$ so $r=3.$ However, the problem asks for diameter, so our answer is $\boxed{6}.$