MyBB Community Forums

I need tabbed categorys for free because The ones Ive seen cost somthing or don't work.

There's only two plugins for that.

1. Tabbed Menu - $10 Subscription @ MyBB Central

2. MyTabs - Very insecure, very exploitable

MyTabs may be used after modifying it - the plugin coder is yet to update it

one may also use the code from below tutorial (though it was for a different purpose)
Tabbed forum with jQuery (multi categories in one tab

MyTabs is that one in the screenshot.