  A cubical Feynman category, introduced by the authors in previous work, is a
category whose functors to a base category $\mathcal{C}$ behave like operads in
$\mathcal{C}$. In this note we show that every cubical Feynman category is
Koszul. The upshot is an explicit, minimal cofibrant resolution of any cubical
Feynman category, which can be used to model $\infty$ versions of
generalizations of operads for both graph based and non-graph based examples.
