vBulletin is the most popular forum software on the web. In fact, it is the widely used. At just under $200 it is also the most expensive, even though $200 is not a lot for what you get. As a result of this cost and its popularity there is a thriving black market for nulled vBulletin. The nulled version of the software is the illegal versions that hackers have removed the registration and licensing information from the script. With the use if these, you are taking a risk using the software and it is certainly not recommended for doing this.