@robbo
Firstly - This is in no way legal advice, I am not a lawyer / solicitor or affiliated or accredited in any legal profession, what is written here is my own opinion based on a lot of research into intellectual property for my BSc degree.
I would advise that before you conduct activity that may well be illegal in your country or the market your are selling into - please seek professional legal advice - asking these questions on a website will unlikely get you the correct answer and you could find it leaving you in quite a legal quandary.
To "legally" sell something that is under copyright you must either own it, in the regards of software this means you either have permission (a license) from the authors or are the author of the work. if you have neither then, as in most countries you would be committing copyright infringement. This is a civil matter in most countries (not a criminal one)
The copyright owners could then prosecute you in civil court for damages, this may include loss of "goodwill" as well as loss of revenue "through lost sales" and in addition to any legal costs.
Again - please seek professional legal advice before conduction your endeavour