I believe socialism has a pretty specific definition: government ownership and control of the means of production. Which is easy to grasp for steel mills, power plants, and hospitals. A bit trickier in the creative economy and the gig economy.
I am aware of the definition and I don't dispute it. But consider for a moment why socialism wants the state to own all means of production.
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.
