What legal implications does this have? You shouldn't be liable for someone illegally using your software. If you store their information they may have some claim against you for locking up their data.
The intent is to not damage anything, but rather to only crash the program itself. This might lead the user to visit a support forum where they will be kindly adivised to purchase a legitimate copy of the software.
However, if I understand correctly, the program is crashed when it overwrites its own memory. That means that at some point it could end up executing random code. Although very unlikely, it is possible that it could execute the equivalent of "remove users home directory" code. A more likely, but less 'punishing' outcome could be the execution of a tight infinite loop. That could be interpreted as a 'denial of service' and thus full under the booby-trap law.