Apache KIE (Drools)

Apache KIE is the new home of Drools, the Java rule engine that pulls business logic out of your code and into rules an analyst can read. The same repo now holds jBPM (workflow), OptaPlanner (scheduling and routing optimization) and Kogito (all of it as Quarkus or Spring Boot microservices). Instead of nested if-statements, you write DRL rules, DMN decision models or Excel decision tables. Apache 2.0 and free.

Drools is a library pulled from Maven Central, so there's no server to babysit. The work is learning DRL and keeping rule sets governed as they grow. A few thousand rules with no owner is spaghetti in a different file.

Support is the only paywall: IBM sells Business Automation Manager Open Editions (formerly Red Hat Decision Manager) and Aletyx sells enterprise builds, neither with public prices. Solo and small teams: free, though plain code is simpler until rules multiply. Larger teams where analysts own fraud or loan logic: free, plus paid support for an SLA.

The catch: it's been in the Apache Incubator since January 2023, and the README warns releases may have incomplete licensing review. Releases are slow (10.2.0 in April 2026). Workflow-first? Camunda is the usual pick.