The Austrian military didn’t just adopt LibreOffice; they actually contributed back to it. Over five person-years of development work went into adding features they needed. Those improvements are now available to everyone using LibreOffice, which is pretty cool.
That’s right, the commission probably isn’t involved on those cases. I interpreted “The EU” literally by including its various components, ie the EU commission, the member states governments, companies and individuals in those countries.
There’s no central “EU government” that decides everything. The EU is not a centralized country, not even a federation. Members states takes many decisions on their own, and often need to approve EU comission proposals.