This means you as a user can contribute to the code that builds slim. From now on, if you would like to see a change in the rom, and add something to the source code, you can push the change yourself in the gerrit. If you're already familiar with gerrit you know it can take a long time for a patch to get published, that's why we added a little quirk to speed things up.
SlimRoms have always been a product of the voice of the community, and now we've taken one more big step further in this direction, to become the rom of the community.
To read the announcement in whole visit: http://www.slimroms.net/
To head straight to the gerrit go to: https://gerrit.slimroms.net/
With all this said we would also like to give a huge thanks to all the users who already contributed using the gerrit.