Informally, Magic Jar is released under the GNU Free Documentation License (GDL), which allows you, as a member of the public, specific rights with respect to redistributing and modifying any of the content found on this site.
Read the GDL: it's very liberal, and the upshot of it is that if people care about the content of Magic Jar, it will always be available to everybody.
Copyright (c) 1999-2000 Shawn Vincent.
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.1 or any later version published by the Free Software Foundation; with no Invariant Sections, with no Front-Cover Texts, and with no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License".