General Rule : If it does not change a .php file, it should be released in vbulletintemplates.com, not in our site.
Exception : If it does not change a .php file and can be applied via a template modification BUT if it is more than a HTML implementation and involves "coding" skills and algorithms, then it is allowed here.
Example: "PHPINCLUDE" template of vbulletin is a special template which parses directly PHP code. So you can even run an independent PHP script that consists of hundreds of lines of code in that template but that implementation wouldn't be labelled as "template modification" although it does not change any .php files. Even if it can be applied via admin cp/template management section, it would technically still be a "hack". Such modifications are allowed in vb.org.
(PHPinclude template mod above is just an example here. I don't mean only modifications in that template is considered as hacks, nor mean every modification in that template is considered as hack.)
I know this can be a bit confusing as it is highly related to the structures of coding but don't mind it too much. If in doubt, ask a moderator and we will let you know if it should be released in vbT.com or in vb.org.