sidetone

Licence

Source-available, and open source in two years.

sidetone is released under the Functional Source License, Version 1.1, ALv2 Future License (FSL-1.1-ALv2). The licence is one page; this is what it says, in plain words.

You may

  • use it, change it, and run it: at home, at work, for your organisation;
  • install and look after it for a customer, on that customer's own server. The licence names this as a permitted purpose:

“…in connection with professional services that you provide to a licensee using the Software in accordance with these Terms and Conditions.”

FSL-1.1-ALv2, Permitted Purpose

You may not

  • offer it to others as a hosted or cloud service that substitutes for it. That is the one use the licence withholds:

“A Competing Use means making the Software available to others in a commercial product or service that: 1. substitutes for the Software; 2. substitutes for any other product or service we offer using the Software…; or 3. offers the same or substantially similar functionality as the Software.”

FSL-1.1-ALv2, Permitted Purpose

And then

Two years after each version is released, that version becomes available under the Apache License 2.0 as well, and the restriction above falls away for it. The grant is irrevocable and written into the licence:

“We hereby irrevocably grant you an additional license to use the Software under the Apache License, Version 2.0 that is effective on the second anniversary of the date we make the Software available.”

FSL-1.1-ALv2, Grant of Future License

Why this one

Free to use. Not free to resell as a service.

The aim was simple to state: anyone may use it and change it, an IT company may run it for its customers on their own servers, and nobody may take it and sell it as a hosted PBX. FSL says each of those things in a clause of its own, and ends where a permissive licence would have begun. A plain MIT licence was considered and set aside, because a licence can always be loosened later but never tightened for what is already released.

Until that second anniversary the accurate word is source-available, not open source. The code is there to read, build, change and run; the one thing it withholds, it withholds for a while.

Third-party software

sidetone is built on Go libraries under the MIT and BSD licences, whose notices ship with it in NOTICE.