Here's legal jira: https://issues.apache.org/jira/browse/LEGAL-399
TL;DR: JMH is GPL + "Classpath" exception, and that exception allows to link JMH with independent modules to produce an executable regardless of the license terms of these independent modules. In other words, no harm is made even if we release `ubenchmark` to Central (or whatever). JMH use would be valid even if Calcite actually required JMH to function. It does not mean I want to use ubenchmark code in something like SqlToRel, but it is for clarification purposes. Vladimir
