**The following guest post is by Maarten Zeinstra from [KnowledgeLand](http://www.knowledgeland.org/). Maarten is a member of the OKF [Working Group on the Public Domain](http://wiki.okfn.org/Wg/publicdomain).**
Works that have fallen into the public domain after their term of copyright protection has elapsed can be freely used by everybody. In theory that means that these works can be reused by anyone for any purpose which includes commercial exploitation. In theory the public domain status increases access to our shared knowledge and culture and encourages economic activities that do not take place as long as works are protected by copyright. In turn the commercial exploitation of public domain works ([for example out of copyright books](http://www.voyantes.net/blog/?p=589)) has the tendency to increase their accessibility.
In practice, however, determining whether a work has passed into the public domain can prove very difficult. This is especially true when attempting to determine the public domain status of content in multiple jurisdictions. As part of the [EuropeanaConnect project](http://www.europeanaconnect.eu/), [Knowledgeland](http://www.knowledgeland.org/) and the [Institute for Information Law at the University of Amsterdam](http://www.ivir.nl/) have developed public domain calculators to determine whether a certain work or other subject matter vested with copyright or neighbouring rights (related rights) has fallen into the public domain. These public domain calculators have been developed for 30 countries (the European Union plus Switzerland, Iceland & Norway) and are available at [www.outofcopyright.eu](http://www.outofcopyright.eu/).
Users can use the calculators (and the underlying [research](http://outofcopyright.eu/methodology.html) published at [outofcopyright.eu](http://outofcopyright.eu/)) to determine the copyright status of works in all these countries. This is the first time that this question has been structurally researched across all European jurisdictions.
The results of this research of national copyright laws show a complex semi-harmonized field of legislation across Europe that makes it unnecessarily difficult to unlock the cultural, social, and economic potential of works in the public domain. Identification of works as being in the public domain needs be made easier and less resource consuming by simplifying and harmonizing rules of copyright duration and territoriality.
Outofcopyright continues to adjust and refine its calculators. It is also researching how to make calculation possible using large datasets like [bibliographica](http://bibliographica.org/), [DBPedia](http://dbpedia.org/), and the [Europeana](http://www.europeana-libraries.eu/web/api) datasets on cultural objects in Europe.
We encourage everyone interested in the public domain to try the calculators, comment on them and re-use the published research. All research and other material on Outofcopyright is available under the terms of a [Creative Commons Attribution-ShareAlike license](http://creativecommons.org/licenses/by-sa/3.0/nl/) and the [software](http://www.outofcopyright.eu/software_description.html) powering the calculators can be reused under the terms of the [EUPL license](http://www.osor.eu/eupl).