Purpose Free and open source software FOSS brings many benefits to digital preservation however it is not free. If the context in which free and open source software tools are created and employed is examined, it becomes clear that the sustainability of any software FOSS, custom or commercial to ensure the preservation of the digital heritage will depend on careful assessment of, and provision for, the costs implicit and explicit entailed in the production and continued employment of these tools. The purpose of this paper is to focus on FOSS and archiving of the digital heritage. Designmethodologyapproach Portico, a notforprofit digital preservation service, explores the costs of FOSS based on its experiences as a working archive with an extremely long time horizon. Findings There are considerable benefits to FOSS, including its openness and the broadbased testing of it in realworld situations. FOSS tools can provide considerable cost savings over proprietary tools. However, FOSS is neither free to use, nor to create, nor to maintain. Digital preservation organizations must inventory not only the FOSS tools in the preservation arsenal, but the network of sustaining tools FOSS and otherwise, documentation, and tribal knowledge that make these tools effectively usable. The risks to sustainability of this network of resources must be assessed, and determine what it will cost to keep them viable. Strategies will have to be considered and implemented for providing the means to sustain these resources. An engaged community of use is the best guarantor of the vitality of any FOSS tool. As that community wanes, it becomes even more essential to capture the significant properties and domain knowledge about that tool. Creators of new software in the digital preservation space have a particular obligation to provide and maintain information about the significant properties of that software. Originalityvalue The paper shows how Portico brings its practical experiences integrating multiple FOSS tools to bear on an analysis of the costs to creating and maintaining these tools over the longterm.

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   |texte=   The economy of free and open source software in the preservation of digital artefacts
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