Regarding runtime dependencies, there is the issue with libraries like https://github.com/typesafehub/scala-logging. This is a wrapper over slf4j, which is often important as a runtime dependency (and there are also different types of runtime dependencies as there are different logging implementations, including ones that go to logstash, i.e. https://github.com/logstash/logstash-logback-encoder
Also is this what we mean when we are talking about runtime dependencies?