Well there is the offer of a library that you are not allowed to resell (I am sure you didnt know about it first). But with this "pm me to know what I sell at all" - approach it feels quite much like you now would try to avoid similar situations by hiding it from public because (at least I do assume this) you are not sure if you are even allowed to resell the other stuff, too.
Long story short: Most developers do not allow resales because you dont own the rights to do that - you just get a license of use directly from the developer which you cant transfer.
So if you should offer something you are not allowed to (no matter if you do know that or not - the law doesnt care here!) it would be an illegal action. It is not just your risk but also a risk for the customer. Personally I would be careful. Its just not worth the trouble.