Licensing is the foundation of true OpenSource. OSS (Open Source Software) is not the same as public domain software - there is always a copyright on OSS that allows the rights within the license to be defended, while the terms of the license are what make the software permanently "free". In a proper OpenSource license, copyright holder can't change the terms (and this is what distinguishes Open Source from Public Domain Source). There are a growing number of OSS licenses, with the general principles being:

• you can modify and use the source code any way you like, as long as you include the complete copyright notices;
• (in some licenses) you cannot restrict this right for others;
• (in some licenses) you have to make your own modifications freely available and point clearly to the original code.
  • NB - this does not preclude a company modifying TWiki for their own ends and NOT releasing the changes - the license only covers what you must do for redistribution. In most western countries, modifications for private use (e.g. within an organisation) can be made without releasing the modifications, as long as no redistribution occurs.

    A good site dealing with licensing & copying can be found at: http://cr.yp.to/softwarelaw.html

    That said, if your company uses TWiki and you modify TWiki, releasing such changes back to the community decreases the Total Cost of Ownership (TCO) of TWiki which relates to the amount of time and effort spent on keeping the system up to date.

    Finally, there are some countries that do not protect copyrights at all, making any license legal, for any purpose and in any way.

The overall "open source" situation is definitely worth spending the hour or two of online reading time it takes to grasp the complete basics. It is NOT complicated - despite a growing number of licenses, and deliberate attempts by some proprietary software companies to attack and obscure OSS licensing and the open source "movement".

Contributors:

• See OpenSource

Wow, popular topic for editing! Refactoring has made it much better...

OpenSource is not just about the GPL, so I've edited the list of characteristics to reflect this - the BSD-like license family does not require you to distribute your changes (viz. Apache and Perl), but it is popular nonetheless. This is why I didn't get into these issues on this page, the idea was a simple page about the benefits of open source without getting into licensing wars.

-- RichardDonkin - 14 Jan 2002

Great topic - I've added the links to the great summary page on cr.yp.to regarding some of the legal aspects of software in general -- specifically the comments about licensing which are only valid if you wish to do things beyond your legal rights that already have in the user's country of origin. For example, if memory serves correctly, someone in the UAE wouldn't need any license at all to do anything (including selling & taking proprietory) with the TWiki code.

This also means that someone can legally create & build TWiki Addons & plugins that are not GPL'd, as long as they are distributed in patch form only. (I personally have problems with the GPL for example preferring something between the GPL & BSD-like licenses.)

-- TWikiGuest - 14 Jan 2002

It's worth noting that misuse of contributions by the TWiki project and "dodgy" implementation of adhering to the license they have from their contributors, along with total lack of remorse by the lead developer has alienated at least one long standing advocate of TWiki.

If a license says you must include an appropriate copyright notice, you MUST include an appropriate copyright notice. No ifs, buts, or maybes - it's not your work - you can ONLY copy/distribute it under the license it is provided to you under. (You do not have to agree with the license - you can choose not to copy/redistribute their work)

-- TWikiGuest - 06 Sep 2003