Also the article mentions that the Larp mentioned here directly used an Open Source relative (competitor?) to Artemis named EmptyEpsilon: https://daid.github.io/EmptyEpsilon/
Artemis Tom is cool and deserves the revenue and has a lot of cool scenarios and stuff out of the box. EmptyEpsilon is when you start to need more customization, down to source level, and GM tools. (The article mentions a lot of what this Larp did was not heavily automated and somewhat directly in EmptyEpsilon's GM tools.)
While not nearly as extensive as what's in the article, it's a first step achievable with a small group of friends.