We forked our ruleset from classic ruleset soon after rules customization with rulesets was introduced to freeciv, around year 2000. Since then the ruleset has been maintained separately. Not only has it got changes that classic ruleset has not, but also classic ruleset has been changed in ways that didn't make it to our ruleset. Despite this differences between the two are moderate. We have not been adding much new features for the sake of new features, but usually changes have been made only to fix some problem we've experinced in our games, and we do have a somewhat bureacratic process to introduce changes.
Variant2 was forked from that ruleset July -13. It's not subject to same process of introducing changes as the ruleset we use, and I'm likely to some degree use variant2 to test new features of freeciv customizability.