It was an old trading card system someone made back in 2007 for Blockland, before .zip Add-Ons for instance. It's premise sort of aligns with Achievements mod in that both can EASILY be exploited, but there's no way around it without removing the fun so they didn't fix that.
This mod probably needs a complete reinvention over repairing of code and such. It was actually INCREDIBLY flawed and such... especially that everyone's cards was made personally by the person who made this, so most people didn't get cards. Maybe have it save peoples attributes and have a little player display in a box? I don't know...