[nicholasjbs]

Copyrights are indeed transferable. In fact, many of the most well-known free software projects rely on this fact (e.g., should they want to relicense, or to make it easier to defend copyright ownership in court by having a single legal entity behind it).

mluiten might be referring to the fact that copyright only applies to "original works of authorship fixed in a tangible medium of expression." (See http://www.copyright.gov/help/faq/faq-general.html)

That is, copyrights don't cover ideas, but creative works in some fixed form (e.g., a painting or a piece of software).