(really flat top/bottom pay ratio too: private E1 gets paid $19k/yr top generals max out at $180k base - I've heard of grads fresh out of master's getting more than that at Google)
Socialism is all about reducing the effect that direct actions and agreements between individuals can have on society as a whole.
Open source is all about direct action and the unplanned dynamics that may unfold as a result.
The point is to directly control the effects of economically relevant actions and not leave it to an emergent dynamic that results from direct actions and agreements between individuals (i.e. the invisible hand).
Socialists think that it is in everyone's best interest if the government plans what work needs to be done, what resources to allocate and under what conditions the product should be made available to users, which directly contradicts the way in which open source software is produced.
In my view, the similarities between the DoD and socialism are lot greater than the similarities between open source and socialism. Any particular open source project can of course adopt a military style command and control structure, but not the open source model as a whole.