Free As In Freedom ■
Revision: 1.8 (2014/12/22)
In section 1.0 we learned that the term 'Free Software' refers to the state of freedom provided by software, not the financial cost of its production or the price one pays to acquire a copy of it. In that case, we are left unsure as to the meaning of the term 'open source', a phrase which is often used in computer related media without specific definition and even heard in relation to other industries which do not include any reference to computer program source code. If the terms are not inter-changeable, then what is the difference?
When we use the term 'open source', there is no implication of 'freedom'. The philosophy of open source is not the same as that of free software. These are two different philosophies (although with many related results) and to understand how the ideals and motivations of 'free software' differ from 'open source', we also need to define open source. While the term is often misused, the OSI (Open Source Initiative) define 'open source' quite clearly:
“Open source doesn't just mean access to the source code.” 
The OSI goes on to specify terms which are beneficial for the 'ease of development' of open source software and was derived indirectly from the criterion for Free Software . There is a lack of emphasis on freedom itself. However, freedom is often present as by-product of 'ease of development'.
While this difference in focus is true, the classification of software licenses is extremely close, “...their definition agrees with our definition in most cases” .
Fig. 1 - This diagram, originally by Chao-Kuei and updated in 2010 by Ineiev, explains the different categories of software. It's also available as an Scalable Vector Graphic and as an XFig document, under the terms of any of the GNU GPL v2 or later, the GNU FDL v1.2 or later, or the Creative Commons Attribution-Share Alike v2.0 or later. 
To clarify, Free Software in almost every case meets the criteria of the OSI's definition. 'Open SourceSoftware' by the OSI definition most often meets the criteria of the Free Software Definition. The Free software Definition is considered stronger and is designed to protect the freedom of the software. The OSI definition is designed to 'make evolution easy' .
The two can, in some situations produce an identical result. However, if the philosophy is different, then could the ultimate outcome also become different? What happens if we forget freedom?
This is how we begin to realise that the philosophy is what remains through time, as the methods of development change. It might seem a small detail at first – what does the philosophy matter if the same short-term result is achieved? However, if we take our eye off 'freedom' and focus on 'ease of evolution', then we may be trying to create freedom, yet end up assisting others in taking freedom away. One example is 'tivotisation'. In this example, open source software produced a non-free result.
The Linux Kernel was released as free software under the GPL v2. Tivo used the Linux kernel, under GPL v2 in an embedded offering that would only allow an 'official' kernel to run. This meant a platform existed that stopped the software being free. Only the vendor-authorised versions of the kernel could be used on the hardware. This meant that the freedoms of the user had been compromised, even though open source software was used. This was a loophole in the GPL v2 that was patched in GPL v3.This shows how the open source philosophy can be contrasting to the free software philosophy.
Free Software: The response of the FSF was that this was unacceptable and sealed up the loophole in GPL v2 by deploy GPL v3.
Open Source: Linux Torvalds failed to move to GPL v3 and said “...people who make their own hardware can design them any which way they want .... I don't care” .
The end user can lose their essential freedoms if we forget about them and get lost in 'easy software evolution'. The motivation of many of us to do what we have done – the expression of our culture is that of freedom, sharing and of collaboration. Many new programmers will think that if they make their code open source or work on an open source project, that they will give the freedoms they enjoy to the users of the software. That is not true in the example above.
If the purpose of our philosophy were purely to make better software ('make evolution easy' ) ,then if we found another way to make software evolution easy, that didn't happen to involve those freedoms, then those freedoms would not be protected. If we forget freedom and instead focus on technical advantages of 'open source' development, then our loyalty may not be as strong when faced with non-free competitive development models which challenge or even perhaps eclipse the advantages of 'open source' development.
The philosophies of Free Software and Free Cultural Works protects our freedoms, regardless of the methods of development, delivery or device.
If we think about why we are really here, it is not because open source development provides us with better, more reliable and secure software. It is because we have the freedom to innovate and to use better, more reliable and more secure software.
Free Software is a philosophy that often leads to 'open source' development. Open source is a development methodology that often leads to 'Free software'.
We must not forget freedom, as this is why we do what we do.
Another problem with the use of the term 'open source' is that is has been heavily abused, outside the OSI's definition. For example, the 'Open Source License Agreement' from System C  is not a Free Software license and it is not an OSI-approved license. However, its authors have chosen to use the term 'Open Source' in its name. If we educate others to use the term 'open source' and be confident in it, then they would be misled in this instance.
We can expect that as Free Software gains more and more popularity, the term 'open source' will be used by a growing amount of non-technical users. What is important is that users understand that it is freedom we need to protect, not simply to use a particular phrase, whatever it is. Words are not enough, understanding freedom is what is required to ensure we make responsible choices.
This is not to say that 'Free Software' hasn't been misunderstood, in
particular in English where the same word may be used for liberty and
for 'without financial cost'. This is not a problem in many other
languages where 'libre' and 'gratis' are two independent words:
In most of these languages, the word for 'free' cannot be confused with 'gratis'. However, in languages such as English which do not reliably distinguish the two concepts, it is important to present the distinction explicitly so that people won't misunderstand.
So, while there is sometimes a misunderstanding that 'Free Software' means 'software without a cost', we can see that internationally, free often really does mean 'freedom'.
 http://opensource.org/docs/osd (Accessed: 2010/06/18)
 http://www.gnu.org/philosophy/open-source-misses-the-point.html (Accessed: 2010/06/18)
 http://www.gnu.org/philosophy/categories.html (Accessed: 2010/06/21)
 http://www.systemc.org/about/org_docs/license/ (Accessed: 2010/06/21)
 http://kerneltrap.org/node/8382 (Accessed: 2010/07/05)
 http://www.gnu.org/philosophy/fs-translations.html (Accessed: 2010/06/21)
Why Open Source Misses The Point of Free Software. Richard Stallman
Available from: http://www.gnu.org/philosophy/open-source-misses-the-point.html
Open Source Defintion
Available from: http://www.linfo.org/open_source.html