Conflict between vBulletin's license and GPL packages/plugins?

[ElfMage]

(Moderators: please move this thread to the appropriate forum if needed).

I have a question for the vBulletin community at large regarding licensing issues between vBulletin + bridges + CMS/Blog packages (or any GPL package).

I am writing a 'bridge' between vBulletin and MediaWiki (https://vborg.vbsupport.ru/showthread.php?t=123273). While doing so, I started researching portals to use in my site (www.luxurywiki.com), and found that some CMS packages are licensed under GPL (e.g. Drupal, E107) and some under LGPL (e.g. Bitweaver).

So, I tried to learn about this and find the implications of writing an 'extension' (plugin) for MediaWiki, which is licensed under the GPL, that would integrate MediaWiki with vBulletin. vBulletin is a commercial software package, copyrighted by Jelsoft, and licensed on an individual basis to the users who purchase such license (this is my understanding).

In this FAQ about GPL: http://www.gnu.org/licenses/gpl-faq.html#GPLAndPlugins; it is stated that if I write an extension (plugin) for MediaWiki, I have to release it under the GPL due to the fact that MW is loading the plugin dynamically and the plugin uses other MW's internal data structure. (I intended to GPL my plugin).

But, according to the GPL, a GPL licensed piece of code cannot rely on another program/library that is not free (GPL or compatible license).

So, I find myself puzzled by the whole situation. MW is GPL, any plugin I write has to be GPL, but this in turn cannot rely on non-GPL proprietary software (i.e. vBulletin).

Am I misinterpreting something here? Does this make any sense? If any of you have any idea please chime in.

(BTW, as you may surmise, I am not a lawyer )