wjb, VBulletin isn't really "open source". People pay for a licence to use VBulletin software. See here:
Is vBulletin open source? - vBulletin Community Forum
However, changes can be made to the software using mods (modifications). See here:
vBulletin Modifications - vBulletin.org Forum
The new repo system of gold stars/cabbages is such a modification (albeit an old one). I expect forum owners can also modify their own sites as they wish. It is up to the owner/s to take that responsibility and risk. Personally, I doubt there is anything needed by TD that isn't already available as an approved mod.