The actual Maven Loader uncompresses and archives the content of the source.jar, but not the pom file
The pom file (and its signatures) should be archived as well, as follows :
release
|_ source.jar (folder)
|_ source files...
|_pom.xml
|_ pom.xml.md5 (etc...)
> actual version is :
>
> release
> |_ source files...