For private use, yes. But you can't give the URL out publically.
Quote:
Originally Posted by vBulletin License Agreement
If you have a valid licence, you may set up an additional test forum in order to test code, template and database modifications. To make this clear to us and our licence verification procedures, place it in a directory called 'testvb' and be sure to password protect it. It must not be accessible by the general public.