Do you know anything about ANYTHING?! lol

Apparently not on many things, and clearly not on this. Having a plumbers license is not and never has been a requirement to work as a plumber. As with many professions and most trades, the majority of pumbers don't carry their own license. Licensing is usually held by the qualified employee(s) of a company, not the rank and file employees. And besides, if you have the right amount of experience, a plumbing license is a test away for you.

Typically, a scab refers to someone who crosses union lines, not someone who doesn't have a license.