European public bodies are moving to open source for a reason that is not cost.

The European public sector open source argument used to be about licence fees. It lost that argument repeatedly, because total cost of ownership comparisons rarely favoured migration once retraining and support were counted honestly.

The current wave is being justified differently, and the new argument is harder to dismiss.

The three stated reasons

Exit optionality. An administration that can move its documents, its mail and its collaboration tooling without a multi-year project holds a negotiating position it otherwise does not.

Jurisdictional control, sharpened by the sovereign cloud discussion. Where software runs and who can be legally compelled to act on the data are now standing questions in public procurement.

And supplier concentration as a continuity risk, treated in the same register as any other single point of failure.

What the migrations show

The successful ones share characteristics. They started with server and infrastructure layers rather than with the desktop. They budgeted training as a major line item rather than an afterthought. And they kept a hybrid state for years rather than promising a clean cutover.

The failed ones almost all attempted a desktop migration on a political timeline, and they failed on user resistance rather than on technology.

The honest cost picture

Open source migration in a public administration is not cheaper in the first years. It is usually more expensive, because the savings are in licences and the costs are in people, and people cost more.

The argument is that the position purchased, independence from a single supplier's roadmap and pricing, is worth that premium. Administrations that made the argument in those terms have sustained their programmes. Those that promised savings have generally not.

What it means for vendors

Proprietary vendors selling into European public sector should expect exit clauses, data portability requirements and open format obligations as standard terms rather than as negotiating points. That shift is already visible in published tenders and it is not reversing.