The Open Source Initiative recognized 18 different licenses as Open Source Software licenses. If a program adheres to one of these licenses, then it can officially be considered Open Source. Each one of these licenses have a time and place in the Open Source world, and each one has it's own unique history. I am going to put all 18 of these licenses on equal ground (even though I adore the GPL), because they are recognized as equals by the Open Source Initiative. So rather than comparing and contrasting 18 licenses in one article, I'll break it up, and review a couple of different licenses each month. The first two I will be evaluating will be the General Public License (GPL) and the Mozilla Public License (MPL).

The GNU General Public License was created by Richard Stallman to protect the legal right of free software. Free software in the eyes of the GNU is having access to all the code a program contains, including code that just links to GPL covered code. When a program is released under the GPL, it indefinitely retains certain attributes. Under the GPL, a program must provide users with the program's source code if asked, and in return, the author may obtain the source code to any modifications made to the program.

If a program is GPL'd, all code must be attainable by any individual who wishes to inspect it. It is important to note that all source must be surrendered. This includes any code that uses GPL code, or is linked to a GPL program. This feature often discourages people who need to include some proprietary software, because they must forfeit the proprietary code, or be in violation of the GPL, and face a lawsuit. Also included in the GPL is a clause designed to protect the author of free software, by stating that GPL software has no warranty.

So to sum up the legal rights you are assigned by the GPL, you must provide a copy of ALL source code upon request, you retain the rights to modify and redistribute the software, and it protects the developer by stating there is no warranty for GPL software. Anyone who is in possession of GPL software is protected by these same rights. So as a user, you are protected by the GPL to the same extent of the programs author(s). You may redistribute the software or modify it, without asking the authors permission, the GPL gives you the permission to do these things.

The Mozilla Public License was created to fix a problem that corporations had with the GNU General Public License. Companies often favor Open Source, but not necessarily Free Software.The definitions of the two terms, could be explained in another article, because they are fundamentally very different. However for our purposes we will say that Open Source, wishes to protect the integrity of free distribution, and receiving a binaries source code, but it doesn't necessarily have to conform to fit the goals of the GNU.

The MPL (Mozilla Public License) provides the same protection as the GPL to code covered by the MPL. The difference here is that the GPL covers any code directly in the GPL program, and also applies to code that links to GPL software. If a piece of code is going to, in any way, utilize or affect the GPL'd program, that piece of code must be released under the GPL. I think this quote from the The Mozilla.Org web site best summarizes what is protected under the MPL.

"However, if you add a new file that does not contain any of the Original Code or subsequent Modified code, it is not a Modification, and need not be made publicly available in source code form. This remains true even if the new file is called or referenced by changes you made in the Source Code, though those changes do constitute a Modification and must be made publicly available in source code form." In the case of Mozilla, the MPL was created to protect third party software developers who wanted to create plug-ins, but did not want to release their proprietary code. Under the GPL, a plug-in must be released as GPL, under the MPL, this is not a requirement.

Software licenses are often interpreted differently, and the legal jargon is often difficult to read. If you feel I have represented any license unjustly, send me an email, and we can discuss these issues further. The License a developer decides to use to protect their code is very important, and they should read thoroughly the license and understand what it protects. If one of the licenses I review in my column should spark an interest in you, I encourage you to read the legal jargon of that license.

I am a firm proponent of the GPL and the GNU organization. I believe in certain freedoms software users should have. The freedom to have access to all source code connected to a binary is very important. Not only does it protect my rights as a software user, but it forces others to open up their code and spreads the philosophies of the GNU.