The Functional Source License (FSL) is a new license developed by Sentry and Codecov to balance user freedom and developer sustainability for Open Source-minded SaaS companies. FSL is an evolution of the Business Source License (BSL), which has two major flaws: a long non-compete time period and too many parameters, making it difficult for compliance departments to approve use of BSL software. The new license streamlines these issues by setting a shorter change date, selecting Apache 2.0 or MIT as the default change license, and defining Permitted Purpose without an additional use grant. FSL aims to provide freedom without harmful free-riding, prioritizing developer sustainability for both companies and the wider Open Source community.