There are two questions there: 1) Is it possible to use third party code with "forbidden" licenses? As you say, the answer is "it is OK for optional modules".
2) What should be the license of `ubenchmark` module? It looks like `ubenchmark` code links to JMH in a way that we can't strip out JMH and replace it with another alternative. Apparently calcite-ubenchmark is published to Maven Central, so it does not look like "a temporary use for tests", but it finds its way to the Apache Calcite release. Vladimir
