If anyone is worried about backs doors, all they need to do is inspect the source.
...which 97% of the community doesn't know how to do, since this is a bitcoin forum, not a coding forum.
A note to buyers: even if you use a nulled license, this tool will state that the domain is not supposed to be using WHMCS. Many people (like me) use this tool and if it's not verified, WHMCS comes after you.