To

Deploy GeoServer jars to the Maven Repository

1. Sign up for commit access and create yourself a codehaus account.
2. Install the AddTrust CA certificate. Instructions here
3. Modify your settings.xml file ( Located under <home directory>/.maven with a default maven install ):

   <settings>
     <servers>
       <server>
         <id>codehaus.org</id>
         <username>USERNAME</username>
         <password>PASSWORD</password>
       </server>
     </servers>
   </settings>

   Where USERNAME / PASSWORD are your codehaus account username / password.

4. Execute the maven command from the root of the GeoServer source tree:

   mvn deploy

More information can be found here.