At the moment, we only prohibit unwanted dependencies in our starters. That serves users well but means that some of our own modules have duplicates of various classes on their classpath. For example, we have a mixture of Geronimo, Javax, Jakarta, and JBoss spec dependencies being pulled in transitively. Users aren't affected as they're generally in the optional configuration which has no effect on consumers. Straightening this out will make the EE 9 migration easier too.