It turned out to be a configuration problem of the assembly-plugin. The problem is that you can specify a finalName for the assembly output files, but in the further maven-lifecycle (for install and deploy) the .zip and .tar.gz files are referred to as attached artifacts. Thus the specified finalName gets lost and the "new" filename is generated from the artifacts details (artifactId and version).
The only way to add our "src" and "bin" suffixes is to set appendAssemblyId to true and to change the assembly-ids to "src" and "bin" respectively. I committed the necessary changes including some config-cleanup on the assembly-plugin and now both assemblies are installed correctly.
NOTE that the final name of the assemblies is now e.g. myfaces-extcdi-assembly-jsf20-0.9.1-bin.zip instead of myfaces-extcdi-jsf20-0.9.1.zip, because maven generates this filename from the project artifactId (as described above).