Nulled is just another name for crack and how I've seen people refer to wordpress addons. (They are under the gnu license, so i'm not sure if it even counts as piracy)
Wordpress is probably the most targeted bit of web software on the planet. Please do not use cracked plugins, which reduce your security even further. As a developer with years of running many Wordpress sites for clients, I can tell you that each of them face hundreds of probing attacks each day, you cannot afford to open any vulnerabilities.
Nice I haven't needed to relicense my ACF since I have a lifetime one but I am awaiting the eventual rug pull like DeliciousBrains did after WPEngine bought and enshittified them. Really feels like they just tried to secure as many "core" plugins for themselves which I'm really wary about.