Well selling it is up to yourself finding a customer
(who is willing to buy an outdated software from an unknow person)

Then you need to contact Conitec to transfer the license oficially.

Some small recent games of mine:
Griefer 4k http://damocles11.byethost9.com/griefer4k.html
Kobold 4k http://damocles11.byethost9.com/kobold.html
Cave 4k http://damocles11.byethost9.com/cave4k.html