You could have at least transformed the inaccessible video form into text.

It seems like they're referring to https://github.com/Batlez/ChatGPT-Jailbroken/, where you can check the source code.

To me it looks like all that does is make some kind of placeholder replacement, and there's some kind of custom prompt storage and retrieval.

Either way, if it does what you expect it to, doing more than intended by the service provider, it only works until they fix some checks or make some UI changes, and they may hold you accountable for evading technical measures to gain more than you subscribed (and paid) for.

Personally, I wouldn't trust integrating a random third party logic on a registered service. At the very least, I would disable auto-updating or copy/fork it.

I don't see them claiming it being "safe to download". I assume you're taking the implication or assumption as advocation and a safety assessment.

Depending on what you mean by "safe", no it's not safe.

I'm not familiar with the ChatGPT service in particular.