Kai A. Hartung

Kai A. Hartung

Business Source License 1.1 (BSL)

The Business Source License (BSL or BUSL) is a "Source Available" license, NOT an Open Source license (according to OSI definitions). It allows users to copy, modify, and redistribute the code for non-production or limited production use, but typically restricts "competing" commercial u...

Elastic License 2.0 (ELv2)

The Elastic License 2.0 (ELv2) is a non-copyleft "Source Available" license created by Elastic (the company behind Elasticsearch). It is NOT an Open Source license by the OSI definition. It was designed to protect software creators from "SaaS-jacking" by large cloud providers while keep...

Sustainable Use License (Fair Code)

The Sustainable Use License (often associated with the "Fair Code" movement) is a "Source Available" license, not a strictly Open Source license (OSI definition). It grants you broad rights to view, modify, and use the software for free—with one critical restriction.

Browser-Based / Local-First

Browser-Based (Local-First) solutions run entirely inside your web browser. There is no server installation, no login, and often no backend database. The application code is downloaded once, but all data creation and processing happen locally on your device.

Managed SaaS

Managed SaaS means the Open Source creator hosts the software for you. You pay a monthly subscription fee instead of managing servers. This is the "Easy Button" for enterprises who have budget but no time.

Extension / Plugin

Extensions (or Plugins) are small software modules that live inside another host application, most commonly a Web Browser (Chrome/Firefox/Edge) or an IDE (VS Code).

Mobile Application

Mobile Applications are native software installed on smartphones (iOS/Android). In Open Source, these are distributed via standard App Stores or privacy-focused repositories like F-Droid.

Language Runtime (Pip/NPM)

Runtime Deployment means installing the application as a library or package using a language-specific manager (like Pip for Python, NPM for Node.js, or Composer for PHP).

Native System (Binary/Linux)

Native Deployment involves running the software directly on the Operating System, either as a Single Binary (common in Go/Rust) or via a system package manager (DEB/RPM). This is the "Bare Metal" approach.

Docker Container

Docker Deployment is the industry standard for self-hosting software. The application comes pre-packaged in a "Container" with all its dependencies included. It runs reliably on any standard server (Linux/Windows) without conflicts.

LAMP Stack (Linux, Apache, MySQL, PHP)

The LAMP Stack is the grandfather of the modern web. It stands for Linux (OS), Apache (Web Server), MySQL (Database), and PHP (Language). It powered the Web 2.0 revolution (WordPress, Drupal, PrestaShop) and remains the most common hosting environment globally.

Kubernetes (K8s)

Kubernetes is an orchestration system designed for high availability and massive scale. It manages multiple containers that talk to each other. It is designed to ensure the software never crashes, even if a server fails.

Single Sign-On (SSO) & SAML

Single Sign-On (SSO) allows your employees to log in using their existing company credentials (Google Workspace, Microsoft Entra ID/Azure, Okta) instead of creating a new username and password. It ties access to your central employee directory.

Data Residency (GDPR/CCPA)

Data Residency refers to the physical geographic location where your data is stored. Laws like GDPR (Europe) and CCPA (California) often mandate that citizen data must strictly be stored/processed within their borders or in countries with adequate protection.

Backup Strategy (3-2-1 Rule)

A Backup Strategy is the protocol for copying and archiving data so it can be restored in case of data loss (hack, corruption, or accidental deletion). The "3-2-1 Rule" is the industry standard: 3 copies of data, on 2 different media, with 1 offsite.

Community Support

Community Support means there is no help desk to call. Support is provided by volunteers or other users on platforms like GitHub Issues, Discord, or StackOverflow. Responses are voluntary, not guaranteed.

Enterprise Support (SLA)

Enterprise Support is a paid contract (SLA - Service Level Agreement) that guarantees a response time. It ensures you have a direct line to the engineers who wrote the code, often including "Priority Bug Fixes" where your issues jump to the front of the line.

Total Cost of Ownership (TCO)

Total Cost of Ownership (TCO) is the calculation of the real cost of software, not just the license fee. For Open Source, it is the sum of: License (usually $0) + Infrastructure (Hosting) + Maintenance (Engineering Hours) + Security Ops.

The "Bus Factor" (Project Health)

The "Bus Factor" is a risk metric that asks: "If the lead maintainer gets hit by a bus (or gets hired by a competitor) tomorrow, will this project survive?" It measures how dependent a project is on a single individual versus a diverse group of contributors.

Data Portability (Exit Strategy)

Data Portability refers to the ability to easily export your data from a system in a standard, usable format (CSV, JSON, SQL Dump) and import it into another tool. It is your "Emergency Exit" strategy.

Open Core Model

"Open Core" is a business model where the core functionality of the software is free (Open Source), but critical "Enterprise" features (SSO, Audit Logs, High Availability) are proprietary and locked behind a paid license.

Foundation-Backed (CNCF / Apache)

This software is owned by a neutral non-profit organization (like The Linux Foundation, CNCF, or Apache), not a single for-profit company. The Intellectual Property (IP) is held in trust for the public.