Apps to Customizable Interface

UMPlayer is a free and open-source cross-platform media player that boasts a built-in search for YouTube and Shoutcast radio, offering a wide range of supported formats and features like automatic subtitle downloads and customizable playback options.

MuseScore is a powerful and free open-source scorewriter software enabling musicians to create, edit, and print sheet music. It offers a user-friendly interface with comprehensive tools for composition, arrangement, and playback across Windows, macOS, and Linux platforms.

DeaDBeeF is a lightweight and highly customizable audio player for Linux and other Unix-like systems. It supports a wide range of audio formats and offers advanced features like audio conversion, plugin extensibility, and comprehensive playlist management, making it a powerful choice for audiophiles and everyday users alike.

TiddlyWiki is an innovative open-source, single-file, non-linear personal web notebook.

Lightning is a comprehensive calendar and task management add-on for Mozilla Thunderbird and Seamonkey, designed to integrate seamlessly with email. It offers robust features for scheduling, task tracking, and synchronization with various online calendar services, enhancing productivity directly within your email client.

FBReader is a versatile and free ebook reader application supporting multiple formats including ePub, Kindle azw3, and fb2. It offers a customizable reading experience across different platforms with features like library management, synchronization, and text-to-speech.

SeaMonkey is a free and open-source internet suite developed by the Mozilla Foundation. It bundles a web browser, email and newsgroup client, HTML editor, and IRC chat client into a single application, offering a comprehensive online experience.

Midnight Commander is a powerful, console-based file manager offering a two-panel interface for efficient file handling. Licensed under the GNU GPL, it's a free software tool for managing files and performing operations like copying, moving, and deleting with ease.

Kubuntu is an official variant of the Ubuntu operating system that replaces the GNOME desktop environment with the elegant and highly customizable KDE Plasma Desktop. It provides a familiar yet powerful computing experience, blending Ubuntu's stability with the visual appeal and extensive features of the KDE ecosystem.

Double Commander is a free and open-source cross-platform file manager with a classic dual-panel interface. It provides essential file management operations alongside advanced features like batch renaming, folder synchronization, and built-in viewers and editors, making it a comprehensive tool for efficiently organizing and manipulating files across various operating systems.

StarDict is a powerful, free, open-source dictionary application that provides swift access to a vast collection of dictionary files. It supports various dictionary formats and offers offline functionality, making it an essential tool for language learners and researchers.

Amarok is a powerful and versatile cross-platform free and open-source music player. It excels in managing large music collections with features like dynamic playlists, advanced tagging, and integration with online music services. Designed for users who seek comprehensive control over their audio experience, Amarok offers a customizable interface and a wide array of plugins.

Krita is a powerful, free, and open-source painting program designed for professional artists and illustrators. It offers a comprehensive suite of tools for digital painting, sketching, image editing, and animation, making it a versatile solution for various creative workflows.

CyanogenMod was a popular, open-source replacement operating system for Android devices, known for its customization options and focus on privacy and performance.