"Gecko Security by Gecko Security would like permission to: act on your behalf"

Hard no. I will never give tools full access to my GitHub.

Please consider using the new style app with fine grained permissions and the ability to pick specific repositories. What you are asking now is way over the top. "Act on your behalf" means you do your scanning as "me" which means you have admin on all my things and all the orgs i a involved with.

Hard no. I will never sign up for tools that do this. it is a huge security risk. And completely unnecessary from your perspective - just implement the proper (new/modern) app flow instead.