Legacy version damaged

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Bit of Context, My mac is an older machine, '09, and is running its latest version possible; 10.13.16 High sierra. So, I downloaded the legacy version. but, it refuses to open.

I received the error message, “Pencil2D” is damaged and can’t be opened. You should move it to the Trash.

Upon going to the expanded message, it read:

The app has been modified, and its code does not match the original [signed] code. The app may be broken or corrupted, or it may have been tampered with. If you think that an app has been damaged or tampered with, you should delete it by dragging it to the Trash.

Some apps and tools, such as AppleScript or JavaScript applications and some legacy tools, modify themselves after signing. These types of apps cannot be opened unless you override the security settings on your Mac. For more information, see Open an app by overriding security settings.

To learn how to protect your Mac from harmful software, see [Protect your Mac from malware]."

I did try the overide btw, it still reads the same error

Little note: both the [Protect your mac from malware] and the [signed] had hyperlinks, but this is a new account, so I had to delete them.

If anyone needs the links, I will be happy to oblige.