OSI-licensed open source
Contact management software stores people and organisations, tracks interactions and keeps details synchronised across devices. In practice it spans two types of tools: full CRMs that manage leads and deals, and CardDAV servers that simply sync address books.
This guide covers five CRM and ERP suites and two lightweight CardDAV servers, so you can match the tool to the scale of the job. Licences come from the project repositories; where a project is open-core, the paid parts are noted.
Tools, licences and pricing checked against vendor and repository pages on November 7, 2026.
| Tool | Best for | Pricing | Licence |
|---|---|---|---|
| SuiteCRM | Established, extensible CRM | Free, open source (self-hosted); hosted and support options - see vendor | AGPL-3.0 |
| EspoCRM | Small-team CRM | Free, open source (self-hosted) | AGPL-3.0 |
| Twenty | Modern, developer-friendly CRM | Free AGPL core (self-hosted); Enterprise Edition requires a subscription - see vendor pricing | AGPL-3.0 |
| Frappe CRM | Teams in the Frappe or ERPNext ecosystem | Free, open source (self-hosted); Frappe Cloud - see vendor pricing | AGPL-3.0 |
| Dolibarr | Small business ERP with contacts | Free, open source (self-hosted) | GPL-3.0 |
| Radicale | Lightweight CardDAV sync | Free, open source (self-hosted) | GPL-3.0 |
| Baikal | CardDAV and CalDAV for self-hosters | Free, open source (self-hosted) | GPL-3.0 |
Best for: Established, extensible CRM · Free, open source (self-hosted); hosted and support options - see vendor
SuiteCRM is an open-source CRM published under AGPLv3.
Best for: Small-team CRM · Free, open source (self-hosted)
EspoCRM is a free CRM for managing leads, contacts, sales, marketing campaigns and support cases.
Best for: Modern, developer-friendly CRM · Free AGPL core (self-hosted); Enterprise Edition requires a subscription - see vendor pricing
Twenty is an open-source CRM. Its repository is AGPLv3 with exceptions: files marked Enterprise use a commercial licence, and production use of those requires a subscription.
Best for: Teams in the Frappe or ERPNext ecosystem · Free, open source (self-hosted); Frappe Cloud - see vendor pricing
Frappe CRM is a fully featured open-source CRM for sales teams, built on the Frappe framework.
Best for: Small business ERP with contacts · Free, open source (self-hosted)
Dolibarr is a PHP application for managing a company or foundation, including contacts, invoices, orders, stock and accounting.
Best for: Lightweight CardDAV sync · Free, open source (self-hosted)
Radicale is a simple CalDAV (calendar) and CardDAV (contact) server.
Best for: CardDAV and CalDAV for self-hosters · Free, open source (self-hosted)
Baikal is a calendar and contacts server built on sabre/dav.
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| If you need… | Start with |
|---|---|
| Full sales CRM | SuiteCRM, EspoCRM |
| Modern CRM with API | Twenty |
| ERP plus contacts | Dolibarr, Frappe CRM |
| Just sync contacts to phones | Radicale, Baikal |
Quick answers to common questions
It stores and organises contact details and interactions. It ranges from address-book servers to full CRMs.
Use a CardDAV server for syncing contacts. Use a CRM if you track leads, deals and activities.
Mostly AGPL, but files marked Enterprise use a commercial licence.
Its main branch is a beta and the stable branch is older, so it was left out; check the project directly.
List it on TechLogHub and we'll review it for this guide.
