Even though the use of Open Source Software (OSS) might seem paradoxical in Defense environments, this has been proven to be wrong. The use of OSS does not harm security; on the contrary, it enhances it. Even with some drawbacks, OSS is highly reliable and maintained by a huge software community, thus decreasing implementation costs and increasing reliability. Moreover, it allows military software engineers to move away from proprietary applications and single-vendor contracts. Furthermore, it decreases the cost of long-term development and lifecycle management, besides avoiding vendor's lock in. Nevertheless, deploying OSS deserves an appropriate organization of its life cycle and maintenance, which has a relevant impact on the project's budget that cannot be overseen. In this paper, we will describe some of the major trends in OSS in Defense environments. The community for OSS has a pivotal role, since it is the core development unit. With Agile and the newest DevOps methodologies, government officials could leverage OSS capabilities, decreasing the Design (or Technical) Debt. Software for Defense purposes could perform better, increase the number of the releases, enhance coordination through the different IT Departments (and the community), and increase release automation, decreasing the probability of errors.