Developer Open Source Tools

Alternative toFastmail

Self-hosted email inbox for custom domains on Cloudflare

• 5,117 GitHub stars
• AGPL-3.0Licence AGPL-3.0

Alternative toHashiCorp Terraform Cloud

Self-hosted Terraform CI/CD that runs natively in GitHub Actions

• 5,056 GitHub stars
• MITLicence MIT

Alternative toAzure Cosmos DB

Multi-model NoSQL database: graphs, docs, and key-value

• 4,995 GitHub stars
• Apache-2.0Licence Apache-2.0
• #Database

Alternative toInternet Download Manager

Multi-network download manager for files, torrents, and magnets

• 4,835 GitHub stars
• MITLicence MIT

Alternative toChatGPT

Control your AI infrastructure with Thunderbolt

• 4,799 GitHub stars
• MPL-2.0Licence MPL-2.0
• #AI Agents

Alternative toSlack

Open protocol for secure, decentralized messaging and VoIP

• 4,716 GitHub stars
• AGPL-3.0Licence AGPL-3.0
• #Chat

Alternative toAdobe Acrobat

Split, merge, rotate, and extract PDF pages for free

• 4,632 GitHub stars
• AGPL-3.0Licence AGPL-3.0

Alternative toPlainID

Move access control out of app code into testable YAML policies

• 4,627 GitHub stars
• Apache-2.0Licence Apache-2.0

Alternative toModerne

Automate code migrations at scale using a pattern-matching DSL

• 4,614 GitHub stars
• MITLicence MIT

InDeveloper Tools

Game-specific HDR mods and shader replacement for DirectX titles

• 4,560 GitHub stars
• MITLicence MIT

Alternative toGoogle Gemini Enterprise Agent Platform

Agentic AI framework for the JVM

• 4,524 GitHub stars
• Apache-2.0Licence Apache-2.0
• #AI Agents

InCustomer Support

Open-source tools that work instantly, no signup required

• 4,511 GitHub stars
• GPL-3.0Licence GPL-3.0