When it comes to open-source licenses, developers have their fair share of choices (GPL, BSD, MIT, Apache, etc.), all of them with their own pros and cons. The same goes for commercial licenses. MySQL founder Michael “Monty” Widenius and his co-founder David Axmark, however, came up with a different model a few years ago: the Business Source License (BSL).
This new license offers an alternative to the closed-source and open-core licenses that many startups choose for their software, and, for the first time, Widenius’s new company, MariaDB, is now using it for one of its products.
In some ways, the BSL is akin to a freemium model for software licensing (with an open-source twist). As Widenius explained to me, the BSL allows developers to set a limit for how many servers/CPUs/etc. their software can run on in production (there are no usage limits for test environments, only production usage). Usage above that incurs a licensing fee.
That sounds like a pretty standard commercial license, but the twist here is that all of the source code is available at all times and the BSL license has an expiration date. After a set amount of time (say three years), the license expires and reverts to an open-source license like the GPL or any other license the developer chooses.