The Business Source License (BSL, sometimes BUSL) is a source-available license, not an OSI-approved open-source license. Source is published and self-hosting is permitted up to use restrictions the vendor sets — typically a revenue cap, or a ban on offering the software as a commercial managed service. The license includes a "change date" clause: 2 to 4 years after each release, that release auto-relicenses to a fully permissive license (most often Apache-2.0 or MPL-2.0). It is favored by venture-backed OSS companies trying to monetize a managed cloud service while keeping the on-prem path open.

In a self-hosting context

Self-hosters can usually keep running a BSL-licensed tool indefinitely as long as they are not building a commercial competing service. The BSL-1.1 tools on os-alt cluster lists every BSL-licensed alternative we track. See the /blog/self-host-license-drama-2026-05/ post for the trade-offs and a list of vendors that flipped from Apache or MIT to BSL post-VC funding.