\begin{abstract} The Brazilian Public Software (SPB) is a program promoted by the Brazilian Federal Government to foster sharing and collaboration on Free/Libre/Open Source Software (FLOSS) solutions for the public administration. On the one hand, Brazilian Public Software has some differences from other FLOSS projects. In particular, the public software is considered a public good and the Federal Government assumes some responsibilities related to its use. On the other hand, the software development principles are the same: the trend towards decentralization in decision-making, information and code sharing, and continuous feedback. In this context, we have designed the SPB Portal, a platform based on the integration and evolution of existing FLOSS tools. Nowadays, it provides several modern features for software collaborative development, helping the Brazilian public administration in sharing its solutions. In this paper, we present this integrated software development platform that was developed for the SPB program by a heterogeneous team composed by professors, master students, undergraduate students, and professionals from FLOSS communities. The development of this platform used several FLOSS applications, providing a non-trivial integration among them. This effort has also produced several new features that were contributed back to these FLOSS applications. In this experience report, alongside the platform architecture, the features, and the user experience challenges, we also discuss our work process, based on agile and free software development practices, and the lessons learned in 30 months of work on the SPB project. \end{abstract} \category{H.5.m.}{Information Interfaces and Presentation (e.g. HCI)} {Miscellaneous} \keywords{\plainkeywords}