I believe that is one of the open issues for Marc4j.   I do not know how 
to push a jar or a new version of a jar to a Maven repo.
I believe Bill Dueber was looking into this just last month when he 
wrote the following to the Solrmarc list:

    I'm trying to get marc4j into maven central, and I don't know who
    owns the domain. If it's one of us, then we can use it. If not,
    well, I'm not sure what we do (except maybe use the github location?)

    Bill Dueber
    Library Systems Programmer
    University of Michigan Library

The last release I did was to merely create the jar in the releases 
sub-directory, and reference it in the README.textile file. That 
emulates the way the releases had been done from the site, 
but its not the right way to do a release.

-Bob Haschart

On 11/13/2013 4:43 PM, Jonathan Rochkind wrote:
> I am a committer, but I have no idea how to do a marc4j release.
> There are some fixes in master repo for marc4j. I can find all the 
> parts of the source code that seem to have a version number and change 
> them. I can make a git tag with the version number.
> But what else is entailed, how do people actually get marc4j?  I need 
> to update maven repo somehow or something? Anyone?