Could you give us a better description of the script in question?  (nulled covers a pretty wide spectrum)  Do you mean simple out of date? No longer supported? Let us know.

Also, just as a general rule of thumb, to protect all the Lunarpages hosting clients, we recommend people install and use the latest version of any script they install.  That is done primarily for a security reason.  People often seek out web sites that use out of date (or no longer updated) scripts, because they could be security risks (with open, un-patched security holes and more). 

I interpret it as meaning a pirated script- i.e. not paid for.

By reading the TOS http://www.lunarpages.com/legal/ and AUP http://www.lunarpages.com/acceptable-use/ you can see that LP could either suspend or terminate your hosting account at their discretion.

I must wonder at why one would consider using a nulled script in the first place. The potential for security breaches alone would seem enough of a reason to avoid such nonsense.