I'm not certain I see the point as all that seems to do is create new game classes with specific mutators enabled. Either way,anyone using this would have to add their new game classes to the types table, or edit the one that is created automatically. There is some documentation on the database tables in the SVN trunk under docs/DATABASE.txt.
Actually the idea behind this is to have more than one map list per game type. You can have a map list for small map, urban maps, maps with low G and so on... and all would be vote-able.
Unlike the version for ut2003 the current version is suppose to advertise on the game browser under the base game type. I have not tried the current one.