Textbook of Linux

Also known as: OSS, FOSS, FLOSS

Open source software is software distributed with its source code under a licence that permits users to read, modify, and redistribute it. The term was coined in 1998 by Christine Peterson and promoted by the Open Source Initiative (OSI) as a more business-friendly alternative to "free software". The OSI maintains the Open Source Definition, a ten-point list of criteria a licence must meet to qualify—free redistribution, inclusion of source code, permission to create derived works, non-discrimination, and others.

Open source and free software overlap almost completely in practice: the GPL, MIT, BSD, Apache, and Mozilla licences all qualify under both definitions. The distinction is philosophical. The free software movement (led by Stallman and the FSF) frames software freedom as an ethical imperative; the open source movement (led by figures like Eric Raymond and Bruce Perens) frames it as a pragmatic development methodology that produces better software through transparency and collaboration.

Linux is the canonical open-source success story. Its development model—a global, volunteer-heavy community coordinated through mailing lists and now git—was considered impossible by conventional software-engineering wisdom, yet it produced a kernel used on billions of devices. Open source is now the dominant model for infrastructure software: compilers, databases, web servers, container runtimes, and programming languages are overwhelmingly open source.