According to the appstore, the commons module is indeed compatible with Mx4, it's just the latest version (4.3.4) that is not. The latest commons version compatible with Mx 4 is version 4.3.2, you can download that by going to "all versions" in your modeler.
In general, we only add new features for the latest modeler version. If there is any specific functionality you are looking for in the Mx4 version of the module, I would suggest filing a feature request for that.
By the way, I agree that the version numbering can be confusing. In fact, we recently discussed implementing exactly what you are suggesting. I'm not sure when this will be ready but it's definitely something we're considering.