Licenses: Commercial, Proprietary, Non-Open source & Open Source

OSS have Open Source License:

Allows: Modification & Redistribution Disallows: Discriminatory or over restrictive access to source code

Copyright: A set of legal protections granted by law

License: How copyright holder grants permissions to licensee/party

Open source operates under/within licensing covered by copyright law

OPEN SOURCE LICENSES:

• Applied to source code as well as compiled binary code
• Commercial licenses don’t override open source licenses. All licenses are important as per requirement

Types of Open Source Licenses:

1. Copyleft License: Requires distribution of source code. Difficult compliance & extensive obligations
   1. Weak Copyleft - LGPL, Mozilla, Eclipse, CPL
   2. Strong Copyleft - GPLv2/v3 , AGPL
   3. Extreme Copyleft - SSPL, NPSL
2. Attribution Style License: Requires distribution of copyright & license. Easy compliance & Simple obligations.
   1. No Copyleft - BSD, MIT, Apache

GPL - GNU General Public License (Original Type of Copyleft License)

• GPL - 1989
• GPLv2 - 1991 - Individual Open Source, Use in Linux Kernel, Most famous currently
• GPLv3 - 2007 - Made to address new issues, limited adoption currently, More complex

ISSUES:

1. Contamination of Source Code -
   1. Merges GPL with non-GPL code & Imposes GPL Terms on other software
   2. Method of interaction either by static linking i.e. direct sharing. Set of routines, external functions & variables that are resolved in a caller at compile time (high risk)
   3. or by dynamic linking like sharing memory spaces. Subroutines of a library are loaded into application program at runtime (moderate risk)