EMQX vs Mosquitto licensing

The Business Source License 1.1 governs EMQX from version 5.9.0 onward, when EMQX merged its former Open Source and Enterprise editions into one offering. The source code is visible and can be read, built and changed, but the license is not Apache 2.0 while a release is under BSL. For a production MQTT service, the practical question is whether your deployment falls inside the production grant. The license allows production use of a single node, provided you do not offer EMQX to third parties on a hosted or embedded basis. Educational and non-profit users also get unrestricted production use for non-commercial purposes. Every release converts to Apache 2.0 four years after it is published, so a version you adopt today becomes fully open source on a fixed date that you can calculate from its release.

Two things in that picture depend on your own setup, not on the license summary. First, counting nodes: from 5.9.0, a cluster of more than one node requires a license file, so a single broker used for production sits in a different position than a clustered deployment. Confirm how your architecture, including any standby or load-balanced nodes, maps to that count. Second, the hosted or embedded restriction: if your product exposes MQTT broker capability to customers, partners or other tenants, or ships EMQX inside your own software, you need a reading of that clause that fits your model. Plan a review of the exact LICENSE text with qualified counsel before you commit, and check the README for current license file requirements, since those terms can change between releases.

Treat the license review as a standing item, not a one-time sign-off. When you upgrade, confirm which release you are moving to, its publication date and whether your node count still fits the grant. Record the decision with the version it applies to, so an auditor or acquirer can see what was approved. If the BSL terms do not fit your model, that is the moment to weigh the Apache-2.0 and BSD-3-Clause options discussed below, knowing that Mosquitto's licensing and clustering model differ from EMQX's.

The main cost of switching brokers later is not the license fee but the migration of everything that hangs off the broker. Before choosing between EMQX under the Business Source License and Mosquitto under EPL-2.0 or BSD-3-Clause, list what would have to move: topic structures and retained messages, the ACL rules that govern which client may publish or subscribe to which topic, the client certificates or pre-shared keys each device carries, and any bridges. Mosquitto's bridge settings are documented in the mosquitto.conf manual, where certificate and pre-shared-key TLS options apply to bridge connections. Those are the places where a move to another broker will touch device firmware, not just server configuration.

Licensing timing matters for long-lived deployments. Under the Business Source License, each EMQX release converts to Apache 2.0 four years after it is published, so the terms that apply to a given version are fixed at its release date. A fleet that runs one release for several years will sit under that release's terms for that whole period. Confirm the publication date of the exact version you deploy, and compare it against your own planning horizon. Mosquitto's dual license does not carry a conversion clock, so the question for that broker is different: confirm which edition, open source or Cedalo's commercial Pro Edition, supplies the high availability or persistent queuing features you may later need.

Re-check the license at every upgrade, not only at purchase. EMQX's single-node production grant and the requirement for a license file once a cluster has more than one node are conditions that can change the cost of an upgrade path that adds nodes. Effort for any migration depends heavily on how much rule engine logic and data integration with external systems the deployment uses, because those flows must be rewritten rather than copied. Measure this on your own deployment by inventorying rules and connectors before you estimate a move, and ask any vendor or implementation partner to quote that work from a written inventory.

Licensing settles whether you may run a broker in production at all, but it rarely settles which broker you should run. The wider comparison, EMQX vs Eclipse Mosquitto, weighs protocol support, clustering and the rule engine alongside the license. EMQX supports MQTT 5.0, 3.1.1 and 3.1, MQTT over QUIC, and gateways for MQTT-SN, CoAP and LwM2M, with a SQL-based rule engine and integrations to more than 50 systems. Mosquitto implements MQTT 5.0, 3.1.1 and 3.1 and is built to stay small, which suits devices from low-power single board computers to full servers. Start with the feature list you need, then read the license against it.

Footprint and topology often decide the broker before the license does. If your design needs a multi-node cluster with masterless clustering, the EMQX license file requirement applies from 5.9.0 onward, so that cost belongs in the architecture review. If your design is one broker per site, bridged upward, Mosquitto's bridge support documented in the mosquitto.conf manual may cover the topology without a cluster license. Confirm with your architects which of these shapes you actually need in year one and in the expected growth path, because switching brokers later means moving clients, topics, authentication and rules together.

Before you sign off on either option, write down four things: the MQTT versions and transports your devices use, whether you need clustering or high availability, which external systems must receive data, and who in your organization owns the license and renewal. Then check each answer against the license terms and the vendor documentation rather than relying on this page alone. If the answers point to clustering with heavy integrations, EMQX's license model is the right place to start the legal and budget discussion. If they point to a single broker with simple bridging, Mosquitto's licensing is usually the simpler conversation.