The software itself does not forcibly stop working after the trial period, but it will display a persistent "nag screen" reminding you to register. It's a system based on trust and the honor system, which has been a hallmark of shareware since the early days of software distribution.

Malicious code that monitors your browsing habits and personal information. 2. Bundled Adware and Browser Hijackers

When you purchase a license from the official mIRC website, you receive a unique registration key tied to your name. This key converts your evaluation copy into a fully registered version, permanently disabling the countdown reminder screen that appears at startup.