I swapped out the default dosbox for my own copy (I think at the time it was daum's SVN version; currently I use dosbox-x), which allowed changing the renderer to opengl/directx/etc. One of these allows the user of steam overlay, though I can't recall which. Iirc it doesn't work completely, but the screenshot hotkey did.

How did u do that?

haha

I love this background.. so minimalistic.. ;p