In the UK overpayments must be paid back legally, probably varies from country to country as you say.
There was no contract as such except the confidentiality contract which I am considering breaking, pending legal advice er.. not that I actually have a lawyer but advice here would be welcome on this matter!
So the $5000 buy promise I believed on good faith, more fool me eh. I am very happy with the site in any case, maybe I can even find another company to match the buy, not sure Ongame will want to do business with the site again!
I just received an email from the company which was not difficult to reply to: Basically they asked if I bought the whole company or just the domain, i.e. ‘should we sue you or not?’ To which I replied ‘no thanks’, it was just a domain transfer, he kept all the aff accounts and stuff.