How do licenses participate in Free and Open Source Software (FLOSS) community life? This paper aims at answering this question. Despite the dynamic character of FLOSS development, the sociological debate has taken for granted a static perspective of communities organized around a restricted range of social values and rules. Criticizing the main sociological approaches to FLOSS community, we assert, on the contrary, that the FLOSS free/open character shall not be assumed a priori to explain the coordination efforts in communities. Focusing on the role of software licenses in everyday FLOSS communities activities, considered as boundary objects, we observe that controversies and conflicts around licenses are fundamental parts of communities life. Basing our researches on two different projects, the Geographical Information System GRASS and the OpenSolarisTM Operating System, we show how the construction of the FLOSS free/open character takes place inside the debates about licenses.