Two main Rights Expression Languages (RELs) exist to describe licenses governing the access to digital content: ODRL (Open Digital Rights Language) and MPEG-21 REL. Both RELs are powerful and complex enough. The use of different RELs could divide the network commerce in two separate factions. In this paper we propose a way for interoperability between them. They have many similarities that permit to translate expressions from one language into the other one. In the Distributed Multimedia Applications Group (DMAG) [12] we are developing utilities that permit to translate licenses between both RELs. Furthermore, the DMAG has developed a set of applications to generate and check licenses in both RELs. This paper first describes the current situation of the RELs. Then the MPEG-21 REL and ODRL are introduced. Later, the interoperability between ODRL and MPEG-21 REL is exposed and the DMAG licenses generator and checker are described1 . 1 Rights Expression Languages At present, network comm...