ns the RAN, UE and EPC implementation. A 5G version of OAI is in development. Despite significant interest in open source, as of now there are no open source NG-RAN implementations yet that are close to being mature enough for commercial deployment. 6.3.2 Market Drivers For operators, open source is yet another way to commoditize the RAN, with an ultimate goal of driving down CAPEX and OPEX and decreasing their dependence on a specific network equipment vendor. For academia, open source RAN is a good opportunity to apply their research to what may eventually become an actual wireless network. Even if that promise does not materialize, open source implementations are perhaps one of the best ways for researchers in the field of wireless communications to test their ideas in the field. While smaller network equipment vendors are likely to benefit from the availability of open source RAN implementation, which may shorten their time-to-market and generally decrease the entry barrier for them, it is not clear if there are benefits to be gained by the established market players. That being said, at least some of them are actively contributing to open source RAN projects. 6.3.3 Open Source License As we mentioned above, different open source projects use different open source licenses, which in turn allow for different levels of freedom to use the software and different limita- tions imposed on its usage. Perhaps not surprisingly, there are hundreds of open source licenses. The Open Source Initiative (OSI) is keeping a list of these, while the Free Software Foundation (FSF) main- tains a list of what it considers free. These organizations are sometimes in disagreement about which licenses should be considered "open" and "free." Licenses that do appear on both lists are sometimes referred to as free and open source software (FOSS). In addition to free VS. open, open source licenses are sometimes categorized as "permis- sive" or "copyleft." A permissive software license generally imposes few to no restrictions on the usage