[bburl] is
not a BBCode. The
bburl bit is the key which is associated with the value for that setting. $vboptions is an array of options, you can read about arrays on the PHP site (
See here).
I think if you hover over the input box for a setting (in the AdminCP) it will tell you the
key name. Otherwise you can run a plugin with [minicode]
var_dump()[/minicode] on [minicode]$vbulletin->options[/minicode] to see a full list of it's contents.