OpnForm vs ETAR
A side-by-side comparison of two self-hosted calendar & contacts options — licensing, setup difficulty, resource needs, and what each one replaces.
Not the right match-up?
| Feature | OpnForm | ETAR |
|---|---|---|
| Category | Calendar & Contacts | Calendar & Contacts |
| License | AGPL-3.0 | GPL-3.0 |
| Language | PHP | Java |
| Setup difficulty | Medium | Medium |
| Min. RAM | 512 MB | 256 MB |
| Deployment | docker | docker, source |
| GitHub stars | ★ 3,545 | ★ 2,565 |
| First released | 2026 | 2016 |
| Replaces | — | Google Calendar |
Why pick each one
Choose OpnForm if…
- Released under the AGPL-3.0 license
- First-class Docker support for quick deployment
- Active community (3.5k GitHub stars)
- Written in PHP
Frequently asked questions
Is OpnForm or ETAR better?
Neither is universally better. OpnForm has the larger community; both share a medium setup difficulty, so the decision comes down to features and licensing.
Are OpnForm and ETAR free and open-source?
Yes. OpnForm is licensed under AGPL-3.0 and ETAR under GPL-3.0. Both can be self-hosted at no software cost.
Can I run OpnForm and ETAR with Docker?
OpnForm: yes. ETAR: yes.