Surely appfuse:full-source is an option, but there are other reasons why one would leave the dependencies. In my case for example, I try to stay up to date with the latest version. Migrating from 3.1 to 3.5 was painless.
If you check for versions prior to 3.5, the *-sources.jar were always there.
Besides fixing the release build, it would still be great to have the 3.5 sources in Maven Central as well.