This document discusses network softwarization and the role of open source. It begins by defining network softwarization as the trend toward more programmable, software-defined networks achieved through SDN and NFV. It then discusses how open source has played a role in networking, particularly through projects that enable network softwarization like OpenDaylight, OpenStack, and OPNFV. The document concludes by discussing some experiences with open source networking projects at UNICAMP like RouteFlow, libfluid, and Mininet-WiFi, which aim to advance the state of SDN and network programmability through open collaboration.