There are several circumstances under which it is legal to distribute copyrighted material or parts thereof.
- Free distribution. Copyright holders may choose to allow free distribution of their works. Dedicated copyright licenses—usable by anyone who wants to upload their own material—are available for that purpose. Such licenses are often used in situations with large numbers of copyright holders, like in online communities. For example, the
Creative Commons license family for
free cultural works in text, audio, video or image format; or software licenses for
Free Software /
Open-source software like the
BSD License and others.
Wikipedia itself can be distributed via BitTorrent for the same reason.
- Public domain. Works that are in the
public domain and therefore not (or no longer) subject to copyright law can also be legally distributed. For instance,
Project Gutenberg regularly collects and publishes classical cultural works after their copyright has expired (which depends on the country in which the work was previously published).
- Fair use. Some countries also have
fair use provisions in copyright law, which allow people the right to access and use certain classes of copyrighted material without breach of the law.
There are also experiments at legally selling content that is distributed over BitTorrent using a "secure" tracker system.