A number of free software proponents, such as Richard Stallman[6] and Daniel J. Bernstein[7], have criticized IEEE's copyright policy. As with most other scientific and technical publishers, when publishing with the IEEE the author is forced to transfer his copyright[8] to the Institute, which then sells the paper in journals and online. Typically, however, scientific and technical journal publishers do not pay authors or the reviewers.[citation needed]
This has prompted the appearance of so-called "Open access" scientific publishers such as the Public Library of Science, which employ different schemes such as charging the author or resorting to advertising, as opposed to charging the reader. However, publishing in IEEE journals is almost mandatory[citation needed] for those operating in the scientific communities of IEEE covered fields: impact factors of IEEE publications are among the highest.[9]