Open source facility management software is searched for by two different people with the same words. One has no budget and wants the license fee gone. The other has been burned by a vendor and wants the building's record somewhere it cannot be taken away. Those are different problems, and open source solves the second one much better than the first. The license is free; the running is not. When you weigh facility management software, open source against a subscription, the honest comparison is not the subscription price but the hours of whoever ends up looking after the server, the backups and the upgrades.
What you actually take on
Somebody has to host it, back it up, restore it once to prove the backup works, apply updates, and hold the accounts when people leave. In a maintenance department that somebody is usually the person who is best with computers rather than someone whose job it is, and their availability becomes a dependency of the building's record. Cost it in hours a month at a real rate before comparing it to a subscription, and include the week where an upgrade goes wrong, because that week always arrives eventually.
What you genuinely get back
The data is in a database you control, in a schema you can read, and no pricing change or acquisition can hold it hostage. For an institution that expects to keep the same buildings for decades, that is worth more than it looks on the day of purchase. You also get to change things: a field the trade actually uses, a report in the shape your board asks for. Whether that matters depends entirely on whether anybody near you can and will do it.
The middle path most single buildings end up on
For one building with a few hundred assets, the usual honest answer is neither extreme: use free tools for the arithmetic, which is where the pressure actually is, and keep the record wherever it can be exported cleanly. The condition index, the backlog by system and the cost of a year of preventive work are calculations, not infrastructure, and they do not need a server. Our worksheets do them on the page from your own figures, free and with no account, which removes the budget argument without adding a machine to look after.
Questions people ask about open source facility management software
Is open source less secure?
Not inherently, but the responsibility moves to you. Patching, backups and account hygiene are yours rather than a vendor's, and an unpatched self hosted system is a worse position than either a maintained open source one or a hosted product.
Can we start open source and move later?
Usually yes, and this is the strongest argument for it: the data is in a readable database, so migrating is an export rather than a negotiation. Check the schema and the export path before you commit either way.
What if nobody here can run a server?
Then treat the license fee as buying somebody to run it. Free software with nobody to maintain it becomes an unbacked up machine under a desk, and the building's record should not live there.