This article presents the findings of a research aimed at characterizing F/OSS migration initiatives, in total 30 experiences have been considered, 19 of which have been conducted by public administrations and the rest by private firms, operating different industries in eight different countries. Open source migration projects is a recent research topic, more so when considering it from a managerial perspective. To overcome the lack of theoretical models an empirical approach relying on grounded theory has been adopted as this inductive approach allows theory building and hypothesis formulation. According to the results, migrating from proprietary into open source is dependent on contextual and organizational factors, as for example, the need of the change itself, the political support for the change, the suitability of IT, the organizational climate, the motivation of the human resources, the kind of leadership for the project or the firm complexity. Besides, migration efforts imply strategic and organizational consequences that the organization must evaluate well in advance.