can we use a private Github to let our devs edit the addons ?

If they leak it, yes. The addon is your responsibility no matter who may do what with it.

Don't do that.

Your chances of getting banned in the end will be high as most ""developers"" just fuck off with your addons and leak them. You shouldn't upload your addons anywhere other than your server for security reasons either.

thank you for your advices :)