Open Source Software
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.
Apache Cassandra
Apache Cassandra is a free and open-source, distributed, wide column store, NoSQL database management system. Apache Cassandra is designed to handle large amounts of data across many commodity servers, providing high availability with no single point of failure. The database has become the choice of many organizations that need scalability and high availability without compromising performance. Apache Cassandra also provides support for replicating across multiple datacenters, providing lower latency for end users of Cassandra-powered applications.
RethinkDB
RethinkDB is a scalable, open-source database designed for real-time applications. When your app polls your database for data, it becomes slow, unscalable, and cumbersome to maintain. RethinkDB solves this by providing a new database access model, where developers can instruct the database to continuously push updated query results to their applications, without polling.
SpeedCrunch
SpeedCrunch is a free and open-source high-precision scientific calculator. The application features a fast, keyboard-driven user interface that displays results as you type. SpeedCrunch comes with over 80 built-in mathematical functions, if that's not enough, you can define your own functions. A library of built-in formulas that allows to you to review and insert commonly used formulas is also included. SpeedCrunch can be downloaded for macOS, Linux and Windows, and is licensed under the GNU General Public License.
Nuclino
Nuclino is a lightweight and collaborative wiki for all your team's knowledge, docs, and notes. Nuclino can serve as your teams collective mind. It includes features like a WYSIWYG collaborative real-time editor and a visual representation of a team's knowledge in a graph. Nuclino allows you to stay connected and effective while on the go.
nomacs
nomacs is a free, open source, cross-platform image viewer. With nomacs you can easily view and manage all common file formats including jpg, png, tif, bmp, raw and many more. The sleek user interface provided by nomacs features a semi-transparent widgets that display additional information such as thumbnails, metadata or histogram.
Elgg
Elgg is an award-winning open source social networking engine that provides a robust framework on which to build all kinds of social environments, from a campus wide social network for your university, school or college or an internal collaborative platform for your organization through to a brand-building communications tool for your company and its clients.
MeshyDB
With MeshyDB you can setup an API backend in minutes. Instead of building time consuming APIs, MeshyDB lets you focus on front-end developerment instead.
Diaspora
Diaspora is a privacy-aware, distributed, open source social network developed by the Diaspora Foundation. The social network is built up of distributed pods, that can be self-hosted by anyone. However, to join the Dispora, you can simply chose an already hosted pod on the network. Members can share and discuss content with others, and label content with hashtags, allowing them to easily follow certain topics that they are interested in. Diaspora also supports @mentions and re-shares of posts, features which all adds up to an intricate communication and sharing system, distributed across the globe.
Debian
Debian is a free and open-source operating system and GNU/Linux distribution that is openly developed by the community-supported Debian Project. The distribution was first released in 1993 and today it is the base of many other Linux-based distribution such as the popular Ubuntu. The project includes over 59000 packages, precompiled software bundled up for easy installation on your machine.