What are the main issues with regards to mashups and copyright law?

Copyright Law - The exclusive rights of the copyright owner over acts such as reproduction/copying, communication, adaption and performance - unless licensed openly - by their very nature reduce the ability to negotiate copyright material without permission.

The permission that is required is that of a voluntary open content licence, Creative Commons licence, or if a statutory licence exists, or obtained straight from the copyright owner.

Mashups raise many interesting and contentious issues with regards to copyright law, with most of the content of these mashups coming from mashups that interface with and utilise information from established companies and web applications. Information is mainly sourced from third parties who have not been given permission and therefore will inevitably encounter legal problems when the whole or part of the original material has been reproduced in some way. It is not uncommon for a mashup to display this information in a manner that the larger entity does not approve of, leading to ethical discussions.

Sometimes, mashups are prohibited by the user agreement of the web site. Ebay, for example, prohibits using their content in this manner through its user agreement.