The Open Directory Project is (not quite , but close enough for government work). Essentially this means that anyone can download and public the directory listings, in whole or in part, for free, just by agreeing to include a brief acknowledgment. For details, see the license, at http://dmoz.org/license.html. This category lists those Web sites that have done so that we have found out about (there might be others, there is no requirement to tell the ODP that you are using the data).
This category lists those 'data users' which concentrate on the Adult category, or are aimed at the Adult orientated market. If the 'data user' is more mainstream, it should be listed in http://dmoz.org/Computers/Internet/Searching/Directories/Open_Directory_Project/Sites_Using_ODP_Data/.