iTop

iTop models IT the way ITIL says to: configuration items, the dependencies between them, and the incidents and changes that touch them. That makes it the closest open source structural match to ServiceNow, and also the most work to set up.

Combodo releases the core under AGPL, free and self-hosted, with the CMDB, ticketing and change management included. Paid editions and the iTop Hub add extensions, connectors and support, sold by quote rather than a published price list.

The dependency graph is the reason to choose it. When a database goes down and you need to know which twelve services just broke, iTop can actually answer that. Snipe-IT cannot. Small teams: overkill. Large teams with a real change-management process: this is the fit.

The catch is the data model. iTop is only as good as what you feed it, and populating a CMDB honestly is a months-long project that never entirely ends. Teams that skip that work end up with an expensive list of servers nobody trusts.