Nulled software refers to a version of a program that has been cracked or modified to bypass licensing restrictions, essentially allowing users to access the software without paying for it. The term "15 patched" suggests that the software has been updated or modified multiple times (in this case, 15 times) to fix bugs, add features, or circumvent security measures. The appeal of such versions is often the cost savings, as users can access premium software without the financial commitment.