Licensing dependencies among open source software (oss) packages reveal a lot about software compatibility relationships and the practicalities of oss licensing. There is, however, limited information on these in the literature. In this paper, we discuss various aspects of oss licensing, and we present an empirical study on FreeBSD ports collections concerning their licensing dependencies, in an attempt to identify specific patterns. Our results highlight different types of dependencies, that could be used to explain, or even guide the license selection process of oss projects.