Mac OS X Softwares to Extensible by Plugins/Extensions

OneSwarm was a file-sharing client focused on privacy and anonymity, designed to operate within a darknet or a friend-to-friend network.

MyBB (MyBulletinBoard) is a free, open-source forum platform written in PHP and utilizing MySQL. It provides a robust and extensible solution for building online communities, offering features like integrated spam protection, user management, and a plugin system for customization.

Speed Dial is a versatile browser extension designed to replace your default new tab page with a highly customizable visual dashboard, offering quick access to frequently visited sites, bookmarks, and browsing history for enhanced navigation and productivity.

ArchiCAD is a powerful BIM software suite designed for architects, engineers, and construction professionals. It facilitates comprehensive building information modeling, design, and documentation workflows for projects of all scales on both Windows and macOS platforms.

Psi+ is a robust, cross-platform XMPP/Jabber client tailored for users who prioritize control, privacy, and extensibility. As a development branch of the classic Psi client, it offers advanced features for secure and customizable instant messaging.

rxvt-unicode, often abbreviated as urxvt, is a highly customizable and lightweight terminal emulator known for its performance and extensive feature set provided through plugins. It's a fork of the original rxvt and is a popular choice for users seeking a fast and highly configurable command-line interface.

Visual Paradigm is a comprehensive modeling and design tool for software development, enterprise architecture, and business process analysis. It supports a wide range of diagramming notations including UML, BPMN, ERD, and more, facilitating code generation, reverse engineering, and team collaboration.

Adobe Bridge is a powerful digital asset management application that helps you organize, browse, locate, and preview your creative assets quickly and efficiently. It is a complete solution for managing photos, videos, and other media files, offering robust features for metadata management, batch processing, and seamless integration with other Adobe Creative Cloud applications.

Mylio helps you organize, protect, and access your photos and videos across all your devices without relying solely on cloud storage. It leverages a unique approach to keep your entire library synchronized and accessible, offering powerful organization, editing, and sharing tools.

WeeChat is a highly customizable, free and open-source command-line based chat client. Designed for efficiency and portability, it supports multiple protocols including IRC and XMPP, making it a versatile tool for connecting to various networks.

Textadept is a powerful, free, and open-source text editor designed for programmers. Focusing on speed and extensibility, it offers a minimalist interface while providing robust features like syntax highlighting, code formatting, and a built-in terminal, all heavily customizable through Lua scripting.

FVD Speed Dial is a browser extension that transforms your new tab page into a visually appealing and highly functional speed dial. It allows users to organize bookmarks, synchronize data across devices, and customize their browsing experience with various themes and layouts.

qutIM is a free and open-source, multi-protocol instant messenger designed for connecting to various networks including ICQ, Jabber, Mail.Ru, IRC, and VKontakte. It offers a unified interface for managing multiple accounts and conversations.

OpenProject is a powerful, web-based open-source project management software designed for teams of all sizes. It offers comprehensive tools for managing projects, tasks, teams, and communication in one centralized platform. Ideal for organizations prioritizing collaboration, flexibility, and data control.

Instantbird is a powerful, cross-platform instant messaging client built on Mozilla's XULRunner, leveraging the robust libpurple library from Pidgin. It supports a wide array of instant messaging protocols, offering a unified chat experience.

Komodo IDE is a powerful and flexible integrated development environment designed for building dynamic web applications.

Qt Creator is a powerful, cross-platform Integrated Development Environment (IDE) tailored for building applications with the Qt framework. It supports C++, QML, and JavaScript, offering a comprehensive suite of tools for designing UIs, writing code, debugging, and deploying software across various platforms.

Light Table is an innovative code editor designed to provide developers with instant feedback and a deeper connection to their code. It offers a clean and customizable interface, focusing on interactive development and visualizing data flow.

Mutt is a highly configurable, text-based email client for Unix-like systems. It offers powerful features for advanced users who prefer a lightweight and efficient email management experience directly from the command line.

Nightingale is a highly customizable cross-platform audio player with a focus on extensibility, featuring a beautiful interface, a wide array of supported formats, and tools like media library management, podcast playback, and integrated web browsing.

CodeLite is a free, open-source, and cross-platform Integrated Development Environment (IDE) designed specifically for C, C++, PHP, and JavaScript (Node.js) development. It provides a feature-rich environment to streamline the coding process for these languages.

Nylas Mail, an extensible open-source email client, offers a unified inbox, robust search, and calendar integration. It supports multiple accounts and provides features like email tracking and undo send, aiming to enhance productivity and email management for users.

Haroopad is a discontinued markdown-enabled document processor designed for creating web-friendly content. It offers a distraction-free writing environment with live preview and syntax highlighting, making it suitable for bloggers, writers, and developers.

ZOC is a professional terminal emulator designed for Windows and macOS. It offers a wide range of terminal emulation types and robust features for secure shell (SSH) and Telnet connections, scripting automation, and file transfers. It's a reliable tool for system administrators, network engineers, and developers.

WordWeb is a comprehensive offline English dictionary and thesaurus for Windows, macOS, iOS, and Android, offering definitions, synonyms, antonyms, and related words instantly from any application.

Pinegrow Web Editor is a powerful desktop application for visually building websites and WordPress themes with live HTML and CSS editing. It combines the speed of a visual editor with the flexibility of a code editor, supporting popular frameworks like Bootstrap and Foundation.

Redaxscript is an exceptionally lightweight and high-performance Content Management System designed for simplicity and speed.

PlantUML is an open-source tool that allows users to generate a wide variety of UML and other diagram types from a simple human-readable text description. It supports sequences, use case, class, activity, component, state, object, deployment, timing diagrams, and more, making it accessible and efficient for technical documentation and visualization.

Org-mode is a powerful and flexible mode for GNU Emacs, designed for note-taking, project planning, to-do list management, and authoring documents. It utilizes simple plain text files with intuitive markup.

Rocket.Chat is a comprehensive free and open-source team communication platform, offering real-time chat, audio/video conferencing, screen sharing, and file sharing. Designed for flexibility, it can be self-hosted on-premises for maximum control and customization, making it ideal for organizations prioritizing data privacy and security.