Why Create Your Own Copy
Giving a script or an app access to your email is usually a bad idea, unless you really trust the other party. Why?
- there is potentially very personal data in your mailbox, which you probably don't want to share with any outsider;
- an evil outsider can get access to most of your other accounts by requesting a password reset; an email is sent with the password reset link, the abuser uses the link in the email and deletes the email afterwards, so you won't notice.
See also, for example, https://www.howtogeek.com/365391/don%E2%80%99t-give-apps-access-to-your-email-even-to-save-money/
The Gmail to Evernote script can read all your email messages. I have always shared the script code, so you could check whether this is not abused. But it would be easy to make a change to the script and inject some abusive code. I would not do that (I hope you trust me), but theoretically, I could get hacked, and the hacker might adapt the script.
Therefore it is safer to make your own copy of the script. You are the owner of the copy, and unless you give others access, no one can change it.
If there is an update to the script, you will be informed, so you can check the new code and update your copy. You can check the code in the new script from the menu: Tools - Script Editor.