Horde Kronolith vs OpnForm
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?
Horde Kronolith
Calendar application from the Horde groupware suite
VS
OpnForm
Beautiful open-source form builder
| Feature | Horde Kronolith | OpnForm |
|---|---|---|
| Category | Calendar & Contacts | Calendar & Contacts |
| License | GPL-2.0 | AGPL-3.0 |
| Language | PHP | PHP |
| Setup difficulty | Hard | Medium |
| Min. RAM | 256 MB | 512 MB |
| Deployment | bare-metal | docker |
| GitHub stars | ★ 10 | ★ 3,545 |
| First released | 2003 | 2026 |
| Replaces | Google Calendar, Exchange | — |
Why pick each one
Choose Horde Kronolith if…
- Released under the GPL-2.0 license
- Written in PHP
- Tiny footprint — runs in 256 MB RAM
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 Horde Kronolith or OpnForm better?
OpnForm is the stronger all-round pick: it has both the larger community and the simpler medium setup. Consider Horde Kronolith if its specific feature set fits your needs better.
Are Horde Kronolith and OpnForm free and open-source?
Yes. Horde Kronolith is licensed under GPL-2.0 and OpnForm under AGPL-3.0. Both can be self-hosted at no software cost.
Can I run Horde Kronolith and OpnForm with Docker?
Horde Kronolith: check the project docs for container support. OpnForm: yes.