The best open source alternative to Salesforce is ERPNext, which is both free and Open Source. If that doesn't suit you, our users have ranked more than 100 alternatives to Salesforce and many of them is open source so hopefully you can find a suitable replacement. Other interesting open source alternatives to Salesforce are EspoCRM (Freemium, Open Source), Crust CRM (Free, Open Source), Mautic (Freemium, Open Source) and Corteza CRM (Free, Open Source).
ERPNext is a free and open-source integrated Enterprise Resource Planning (ERP) software developed by Frappé Technologies Pvt. Ltd. and is built on MariaDB database system using a Python based server-side framework.
Crust CRM is a 100% free and open-source CRM. It's fully featured and includes rich dashboards, automation rules (workflows), collaborative team messaging and much more. You can customise your CRM with the included low-code development platform.
Mautic is marketing automation software (email, social, & more). Install on your own website or create a free hosted account. The simple 3-step setup process takes less than 5 minutes and you'll be ready to reclaim control of your marketing.
Corteza CRM is an advanced Free and Open Source Customer Relationship Management platform. Feature rich, a cloud scalable architecture and entirely modular, Corteza CRM allows any organisation to create the CRM environment tailored to their context.
SuiteCRM provides an enterprise-grade Customer Relationship Management (CRM) application to a global community of users and software developers. It is a robust and credible alternative to Salesforce, Microsoft and the major CRM vendors.
Crust Service Cloud is a free, open-source and self-hosted customer service desk, built on the Crust Low-Code platform. It enables businesses to deliver faster and more personalised service to their clients, across multiple channels.
Millennium Business Suite Anywhere (BSA) is web based ERP/CRM solution with integrated BPM. Millennium BSA automates resources' planning (MRPII), distribution, inventory, payroll, HR, purchase, sales. Millennium BSA is distributed under GPL V2.