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Business Source License (BSL)

The Business Source License (BSL) is a source-available license that allows free use with specific limitations and automatically converts to an open source license after a set time period.

What is the Business Source License (BSL)?

The Business Source License (BSL) is an innovative source-available license created by MariaDB founder Michael "Monty" Widenius. The BSL implements a unique time-delayed approach to licensing: it begins with source-available terms that include commercial use restrictions, but automatically converts to a specified open source license (typically GPL or Apache) after a predetermined period (usually 3-4 years).

This temporal approach creates a middle ground between proprietary and open source licensing models, allowing software creators to monetize recent versions while ensuring all code eventually becomes fully open source. The BSL is sometimes referred to as a "time-delayed open source" model.

Key Features of the BSL

The BSL has several distinctive characteristics:

1. Time-Limited Commercial Restrictions

The BSL imposes specific "Additional Use Grant" limitations that typically restrict using the software to compete with the licensor's commercial offerings. These restrictions automatically expire after a specified "Change Date" (typically 3-4 years from release).

2. Guaranteed Open Source Conversion

On the Change Date, the license automatically converts to a specified open source license (the "Change License"), with no action required by the licensor or users.

3. Source Code Availability

Throughout both the restricted and open source phases, the complete source code is available for viewing, modification, and non-restricted uses.

4. Customizable Use Grants

Licensors can define the specific restricted uses in the "Additional Use Grant" section, allowing customization to their business model.

BSL License Structure

A BSL license typically contains these key sections:

  1. License Parameters: Defining the licensor, licensed work, additional use grants, change date, and change license.

  2. Additional Use Grant: Specifying what commercial uses are permitted during the restricted phase.

  3. Change Date: The date when the license automatically converts to the specified open source license.

  4. Change License: The open source license that will apply after the Change Date (commonly GPL or Apache 2.0).

  5. Standard BSL Terms: The core legal text that defines the mechanics of the license.

Example BSL License Text