PLUS is the Picture Licensing Universal System.
"The PLUS Coalition is an international non-profit initiative on a mission to simplify and facilitate the communication and management of image rights. Organized by respected associations, leading companies, standards bodies, scholars and industry experts, the PLUS Coalition exists for the benefit of all communities involved in creating, distributing, using and preserving images. Spanning more than thirty countries, these diverse stakeholders have collaborated to develop PLUS, a system of standards that makes it easier to communicate, understand and manage image rights in all countries. The PLUS Coalition exists at the crossroads between technology, commerce, the arts, preservation and education.”
It is a consortium that has focused on developing standard vocabularies for creating licenses, aimed mainly at creators and publishers of images. The data is similar to ISO REL and ODRL. They have developed some tools, including a PLUS License Generator.
Consult http://ns.useplus.org/ for more techhnical details on PLUS.
PLUS has a relationship with IPTC
It works nicely for embedding restrictions in binaries.For really simple situations, it works perfectly. However, for more flexible or more complex situations, our requirements go beyond what PLUS is able to do.