This implementation of commons-logging uses a commons-logging.jar specific to a particular logging framework, instead of discovery. This takes out the guessing, is simpler, faster and more robust. Just like you chose a logging implementation, you should also use a matching commons-logging - for example you download log4j.jar and commons-logging-log4j.jar, or use jdk logging and use commons-logging-jdk.jar.
A similar packaging is used by Eclipse SWT - they provide a common widget API, but each platform uses a different implementation jar - instead of using a complex discovery/plugin mechanism.
This package generates commons-logging-jdk14.jar - i.e. the java.util implementation of commons-logging api.