Few things;
Most nulled vBulletins that I know of are not getting reported anymore, because
http://piratereports.com is no longer in server as they're no longer corroborating with vBulletin; Therefore might not seen any reports, now doesn't mean people might report you to vBulletin directly.
but if that so happens; The simplely tell you in the e-mail, please remove all files related to vBulletin or purchase a license.
Once purchased; If you're using the same version as latest; then don't upgrade, wait for an update to override with legit files, I've had a few clients who had this problem and they decided to actually purchase vBulletin and I've helped them successfully upgraded to 'nulled' to 'legit' without loosing anything.
This goes for any licenses.
Now if you don't have any money, either find a partner and specificly state you're looking for a partner to 'invest' into a website and how much you're looking for; Let them know if the site will generate sales from ads, shop or subscriptions to see how he/she can make a return and how long.
or take a look on Digital Point or WHT for vBulletin Licenses sold cheap and try to save...anything over $200 might as well buy your own license instead of going thru all the hassle of transfer of ownership; Lastly, don't buy suite...buy forum and you can install the free vBulletin CMS plugin and have the same thing...
or just install SMF as I believe the plugins are setup the same way as vBulletin; Download and import; installed and done. I'm not sure though.