canvas-lms

Canvas LMS is what universities and K-12 schools actually use. It's the open source version of the same platform that Instructure sells commercially to thousands of educational institutions.

AGPL-3.0, written in Ruby on Rails. You get the full LMS: course management, a gradebook, discussion boards, a calendar, file storage, video conferencing integration, and LTI (Learning Tools Interoperability) support for third-party tool plugins.

Self-hosting is free under AGPL. Instructure sells the hosted version (Canvas Cloud); pricing is per-institution and not publicly listed, but think five to six figures annually for universities.

The catch: self-hosting Canvas is a serious undertaking. It requires Ruby on Rails, PostgreSQL, Redis, a job queue, file storage (S3 or local), and real ops knowledge. The AGPL license means any modifications you make must be open sourced if you offer it as a service. And without Instructure's support, you're on your own for updates, security patches, and integration issues. This is enterprise software that happens to be open source, not a weekend project.