Open Source Software for Android
GDevelop
GDevelop is a 2D cross-platform, free and open-source game engine that takes visual programming to the next level. GDevelop allows you to take read-made behaviours and add them to your game objects or create new once with intuitive and east to use events. With GDevelop, it is easy to make games for PC and Mobile, as well as launch HTML5 games playable right in your web browser.
SQLite
SQLite is a free and open-source relational database management system that implements a small, fast, self-contained, high-reliability, full-featured, SQL database engine. Rather than being a typical client–server database engine, SQLite is self-contained and can be embedded into applications. Making it perfect for development frameworks that want to provide a default database without setup, or applications that needs an embedded database. SQLite is built into all mobile operating systems and most computers and comes bundled with a countless applications. SQLite is also ACID-compliant and implements most of the SQL standard, generally following PostgreSQL syntax.
ownCloud
With ownCloud, organizations can collaborate and be more production on their own secure enterprise file sharing (EFSS) platform. The ownCloud platform is self-hosted and allow for secure file sharing within an organization. The platform can be hosted on premise or on a cloud instance, controlled by the organization. The software is written in PHP and Javascript and is fully open source, released under the AGPLv3 license. ownCloud can run on most server hardware and operating systems, and the client for accessing ownCloud is available for Android, iOS, macOS, Linux and Windows.
Opera Touch
Opera Touch is web browser that is made to be used on the go. It features an award-winning, fast web search interface and is the perfect companion for your Opera computer browser. The modern user interface of Opera Touch has been awarded the prestigious Red Dot Communication Design Award 2018. With Opera Touch you can keep your favorites and browser history in sync with your desktop-based opera browser. Allowing you to move from stationary to mobile in seconds.
Qt
Qt includes everything you need to build cross-platform applications that run on various software and hardware platforms such as Linux, Windows, macOS, Android or embedded systems with little to no change in the underlying codebase. Qt is released open-source under the GNU Free Documentation License, and provides a commerical offering for enterprises.
Seafile
Seafile is an open source file sync & share solution designed for high reliability, performance and productivity. Sync, share and collaborate across devices and teams. Seafile can be self-hosted, or provided as a managed and hosted solution. With Seafile, you can rest assured that your files are safe as all files are encrypted before syncing with the server, even system administrators have the capability to view your personal files.
VLC Media Player
A free and open-souce cross-platform multimedia player software and streaming media server. VLC Media Player has been developed openly since 2001 by the VideoLAN project and is available for desktop and mobile devices. VLC Media Player is most commonly use to view videos and movies locally on your devices.
FitoTrack
FitoTrack is a mobile app for logging and viewing your workouts. FitoTrack can show you the most important information, with detailed charts and statistics for your running, cycling and hiking. FitoTrack is available for all mobile devices that use Android or iOS.
Perkeep
Perkeep is a set of free and open-source formats, protocols, and software for modeling, storing, searching, sharing and synchronizing data in the post-PC era. Data may be files or objects, tweets or 5TB videos, and you can access it via a phone, browser or FUSE filesystem. Perkeep is openly and actively developed and anyone is free the contribute to the project.
Joplin
Joplin is a free and open source note taking and to-do list application. Joplin can handle large number of notes organised into notebooks and allow you to write memorable notes using markdown. With Joplin your notes are searchable, can be copied, tagged and modified either from the applications directly or from your own text editor.