How do people know you have a leaked addon

I was browsing gmodstore the other day and on one addon there was something that got me thinking, "if you find someone that is using the leaked version of this addon" how will people know if you have the bought or the leaked version?

Generally, leak authors may can place theirs names like, "leaked by smb" etc, it can happen by this way

I mean some of them can be obvious by having exploits.

old ass versions, errors, too many "paid" addons
but who cares tho
not everyone can afford to buy for scripts in dollars.
too much $$$

Stupid server builds with thousands of gmodstore addons and no owner's code skill.