I dunno what ipanel uses, but vb and ipb dont use smarty, vb for sure have their own template system, and it works - now at least - but its still a waste of time, and would be more user friendly if they used something as well documented as smarty ...
None of the template systems I have seen are as good as smarty is, for some time I avoided using it myself, I thought it was bloated and over the top, then one time I was forced to use it to fix a site and OH MY GOD, it just made what could have been a total headache a breeze, the syntax made sense to me already without reading documenation, you can embed actual php in your templates, it can cache templates ( it actually converts your .tpl docs to .php with real code ) so it doesn't slow anything down, you can use foreach and other smarty specific loops in your templates ( fantastic feature ) you can use php is_* and actual operators in expressions, you can do if else constructs, format dates, generate date / time dropdowns, they really did think of everything, it's well worth anyone who does even a few projects looking at it and learning how it works, suddenly you have 3x the amount of time for actually programming stuff instead of pissing about with html and templates ...