Most of these movies are freely available to own, copy and distribute since they are in the public domain.

That means that the copyright on the films have expired or the films are contributed to the public for viewing without charge or royalties by the author/producer.

U.S. Copyright

A creative work is said to be in the public domain if there are no laws which restrict its use by the public at large. For instance, a work may be in the public domain if no laws establish proprietary rights over the work, or if the work or its subject matter are specifically excluded from existing laws. Because proprietary rights are founded in national laws, an item may be public domain in one jurisdiction but not another. Some works of literature are public domain in the United States but not in the European Union and vice versa, according to Wikipedia.

All copyrights and patents have always had a finite term, though the terms for copyrights and patents differ. When terms expire, the work or invention is released into public domain. In most countries, the term for patents is 20 years. A trademark registration may be renewed and remain in force indefinitely provided the trademark is used, but could otherwise become generic.

Copyrights are more complex than patents; generally, in current law, the copyright in a published work expires in all countries (except Colombia, Côte d'Ivoire, Guatemala, Honduras, Mexico, Samoa, and Saint Vincent and the Grenadines) when any of the following conditions are satisfied :

• The work was created and first published before January 1, 1923, or at least 95 years before January 1 of the current year, whichever is later;
• The last surviving author died at least 70 years before January 1 of the current year;
• No Berne Convention signatory has passed a perpetual copyright on the work; and
• Neither the United States nor the European Union has passed a copyright term extension since these conditions were last updated. (This must be a condition because the exact numbers in the other conditions depend on the state of the law at any given moment.), according to Wikipedia.

When a document or media file is in the public domain, then anyone can obtain a free copy. Movies in the public domain can be edited, mashed into other movie productions, burned onto CDs and DVDs, and freely distributed to the public.

British Law and copyright

British government works are restricted by either Crown Copyright or Parliamentary Copyright. Published Crown Copyright works become public domain at the end of the year 50 years after they were published, unless the author of the work held copyright and assigned it to the Crown. In that case, the copyright term is the usual life of author plus 70 years, according to Wikipedia.

Links to information on Public Domain and Free PC Movies

Proof of Public Domain: http://www.pdinfo.com/proof.htm
Union for the Public Domain: http://www.public-domain.org/
A reference to identify public domain material: http://www.pdinfo.com/
Wikipedia: http://en.wikipedia.org/wiki/Public_domain
Creative Commons: http://creativecommons.org/licenses/publicdomain/

Other Public Domain Resources
http://www.pdinfo.com/proof.php
http://www.desertislandfilms.com/
http://www.openflix.com/
http://www.publicdomaintorrents.com/
http://www.publicdomainflicks.com/
http://pdmdb.org/
http://retrofilmvault.com/
http://www.fesfilms.com/masters.html
http://www.moviesfoundonline.com/public_domain.php
http://emol.org/movies/faq/publicdomain.html