In the context of software, "nulled" refers to a version of a script or software that has been modified to bypass or remove licensing restrictions, copyright protections, or other limitations. In other words, a nulled script is a cracked or pirated version of the original software, often distributed for free or at a reduced cost.
The person who "nulled" the script likely didn't do it out of kindness. They often embed backdoors or malicious code . While Alex sees banners moving, the script might be secretly stealing his users' data or injecting its own ads into his site to make the cracker money. Banner Exchange Script Nulled Definition