Proprietary or Free and Open Source Software

Software also differs in how it is released and licensed — whether you can see its source code, whether you must pay for it, and what you are allowed to do with it. Three categories matter here: FOSS, freeware and proprietary software.

Free and Open Source Software (FOSS)

Some developers provide both the software and its source code freely to the public, with the aim that everyone can develop and improve it further with each other's help.

• Example: the source code of the operating system Ubuntu is freely accessible — anyone with the required knowledge can improve it or add new functionality.
• More FOSS examples: Python, LibreOffice, OpenOffice, Mozilla Firefox.

The defining feature is the open source code — the software is not just free to use, it is open to inspection and modification.

Freeware

Sometimes software is freely available for use, but its source code is not available. Such software is called freeware.

• Examples: Skype, Adobe Reader.
• Free to use, yes — but you cannot see or modify how it works, so it is not open source.

Proprietary software

When software has to be purchased from a vendor who holds its copyright, it is proprietary software.

• Examples: Microsoft Windows, Tally, Quickheal.
• The vendor controls the software; users buy the right to use it.

What decides the category? …