Shane is way better than me @ reviewing resources, so listen to him.

You DO need to know that u gotta put the %%s around skript placeholders when in var names? Right?

Before I get into the review, I want to make note of something here. The dev originally posted this code, got a few bad reviews based on the bad code... they deleted it and are now posting it again.

This script doesn't work, and there a few reasons why:

1) First of all, I want to explain this is NOT a captcha system. When you are told to complete the "captcha", you are actually sent thru a serious of websites which the dev of this uses in hopes to make money. you have to click several lines before you are finally sent to a pastebin site
(link = https://pastebin.com/jEG8sXy0 ... if you wanna check out what it is)
From here, you copy/paste the verification code... yes you heard that right, verification code, not captcha, into chat on the server.

2) The main reason this doesn't work is due to the lack of basic Skript knowledge. The dev uses ONE variable, which is global. Meaning if ONE player completes the "captcha" the rest don't have to do it. As soon as one player joins and completes the "captcha", a global var is set to true, and no one else will actually have to do the captcha.
you can see this in the code:
""
set {captcha.player's uuid} to true
""
notice how its a global var, the same for ALL players?

Another issue stemming from this, when a player quits:
""
on quit:
delete {captcha.player's uuid}
""
the global var is now deleted, so no one on the server will be able to chat until SOMEONE completes the "captcha"

tl;dr:
It doesn't work, due to it being poorly written.