weblate

Weblate is a web-based translation management platform. Translators log in, see the strings that need translating, and work through them with built-in quality checks, machine translation suggestions, and version control integration. GPL v3. Integrates directly with Git, GitHub, GitLab, and Bitbucket; translations sync automatically with your repo. Built-in glossary, translation memory, quality checks (missing plurals, inconsistent translations), and machine translation via DeepL, Google, or LibreTranslate.

Self-hosting is free. Docker Compose is the recommended setup: Weblate, Postgres, Redis, and Celery for background tasks. Ops burden: moderate. Updates, database maintenance, and managing translator accounts take 3-5 hours/month.

Weblate.org offers hosted plans: free for open source projects (with attribution), then $42/month (Basic, 1,000 strings), $155/month (Medium, 10,000 strings), and $380/month (Advanced, 100,000 strings) with enterprise plans above that. Solo developer with a small project: hosted free tier if open source, or self-host. Small team: $42-155/month hosted or self-host to save. Medium to large: self-host likely cheaper, but factor in ops time at your hourly rate.

The catch: the GPL v3 license means any modifications you make to Weblate itself must be open-sourced. For most users (who just run it), that doesn't matter. The self-hosted setup has real dependencies; it's not a single binary. And the UI, while functional, looks dated compared to newer translation platforms.