The notes describe Geolog as infrastructure with persistent, append-only storage and an interactive REPL, not just as a one-shot solver. Datomic's immutable fact model lines up well with that storage story.
The Geolog notes are clear that the system goes beyond plain Datalog.
Geolog needs chase behavior that can:
* invent fresh witnesses for existential conclusions
* branch when a rule concludes a disjunction
* merge terms when equations force equality
Those are central to the chase-based model described in the notes, and they are not features Datomic gives you as a database. Datomic gives you a temporal fact store plus Datalog query tools; it does not give you a geometric-logic engine.
That means a Datomic-based Geolog would still need its own:
* rule compiler / evaluator
* model-branch management
* equality class machinery
* fixpoint / chase scheduler
* termination controls and bounds
Inference: Datomic is a reasonable substrate for storing models and derivation history, but it is not a substitute for the core Geolog runtime.
As of March 26, 2026, Datomic's official docs say that all editions are free and that the binaries are licensed under Apache 2.0, while Datomic's own FAQ says it is not open source because the source is not published.
That source-unavailable dependency has real engineering consequences:
* you cannot inspect or modify Datomic internals
* you cannot self-maintain a fork if Nubank stops investing in it
* debugging deep engine behavior depends on vendor docs and black-box observation
* fully reproducible "build everything from source" workflows become weaker
* some contributors will reject the stack on principle because it is not fully open
So the licensing issue is not "can it legally coexist with open parts of the stack?" The answer there is mostly **yes**. The more important question is strategic:
If Geolog wants the strongest possible open-source story, Datomic is a poor fit. If Geolog mainly wants a strong immutable fact store and accepts vendor dependence, Datomic remains viable.
