These Licenses allow users to view the source code , modify it and often distribute it. However they can have varying degrees of freedom and obligation.
Types of Opensource Licenses:
MIT License(MIT):
Permissive license originating at MIT in late 1980’s.
Allows for reuse in any project (even proprietary ones).
Only requirement is to include the original copyright and license notice in any copy of software.
example: jQuery, Ruby on Rails , TypeScript.
GNU General Public License(GPL)
Ensures that any derivative work will also be opensource.
Its Often described as a copyleft license.
Different versions of GPL with most recent being GPLv3.
example: Linux kernel etc.
GNU Lesser General Public License(LGPL)
Similar to the GPL but with exceptions that allow it to be linked with non-free software.
Example: OpenAI etc.
Apache License 2.0
A permissive license that also provides an express grant of patent rights from contributors to users.
Example: Elasticsearch etc.
BSD Licenses(Berkley Software Distribution)
Permissive Licenses similar to MIT license .
Most common are 2-Clause and 3-Clause(New or Revised) licenses.
Example: FreeBSD , OpenSSH , Redis , SQLite etc.
Mozilla Public License 2.0 (MPL)
A week copyleft license that allows integration into proprietary software as long as the files covered by the MPL remain open source.
Example: Mozilla Firefox , Rust etc.
GNU Affero General Public License(AGPL)
Similar to GPL but it also covers use over a network , suitable for Web Application.
Example: Nextcloud , MongoDB (till v3.6).
Eclipse Public License(EPL)
An open-source license used by many projects at the Eclipse Foundation.
Example: Eclipse IDE etc.