This post started life as a comment to a question on lockergnome.
Given that Lockergnome’s audience is different from mine, I thought I’d better summarise a few points for a non-technical audience. The IT crowd will, I hope, forgive a hint of simplification in the interests of making this quick.
Microsoft Windows (in all its versions) is an example of an Operating System. It provides a common platform so that programmers can write programs – Word, Excel, Internet Explorer, Firefox, Chrome, or whatever. Windows is controlled by Microsoft who pay the programmers, and charge a licence fee to anyone who wants to run Windows. (Microsoft, by the way, also control Word and Excel on the same basis, and Internet Explorer, though they don’t charge a separate licence fee for that.)
Linux is a competitor to Windows, in that it is also an Operating System. However, that vast majority of Linux installations are run with a different model to the “charge a licence fee” model. In that, people are allowed to run Linux, and, unlike with Windows, given the “source code” that allows them to change the underlying bits of it. However, if they do so then they have to give anyone who uses those changes the source code so that those third people can make further changes (and explicitly give them the legal rights to do so, subject to the same “if you change and pass it on, you have to pass on the rights and responsibilities” clause.)
Because of this, Linux has established itself as the dominant operating system in many environments, and the majority of web servers run it in some flavour or another. Most (but not all) programs that run on Linux are licenced in the same way – no fee, but open source code with the obligation to share the rights and responsibilities if you change it.
At this point we re-join the original question….
We’ve got to be careful to understand what a Distro is.
To slightly simplify, a Distro is simply a version of Linux with a different set of installation pre-sets, and a different choice of software installed over the base system. The same occurs in the Windows world – while the underlying Windows XP / Vista / 7 is shipped, different PC manufacturers (OEMs) will pre-install a different set of software. In the Windows world, these pre-installed software choices are normally down to commercial pressures – which ISP will offer the most to have their logo as a “click here to set up XXX” on the desktop, which anti-virus software will offer the PC manufacturer the biggest kickback to have a 30-day trial of THEIR anti-virus pre-installed.
In the Linux world, the pressures are different. While SOME distros are based on commercial pressures, others are based on a wide variety of different models. Generally what happens is that a distro exists, and then some group of people want it to evolve a certain way… while another group want it to evolve in a different way. In the Windows world, there are hierarchical mechanisms, mostly within Microsoft, to decide which set of choices will dominate – in the Linux world, however, in most cases, the minority group of geeks can take the base they like, let’s call it MarksLinux 1.0, and see what happens – they can decide to make “DavesLinux 1.1” if it turns out that “MarksLinux1.1” doesn’t evolve in the way they’d hope. To a certain extent, comparing Linux to Windows is, if you’ll pardon the pun, comparing apples with oranges.
In some respects, the Linux world more closely resembles the ENTIRE I.T. ECONOMY, in that there isn’t one central control, but a whole bunch of different people / organisations releasing competing products. On that basis, asking “Why are there so many Distros” is like asking “Why are there so many operating systems?”
There are many Linux distros for the same reason that there is a choice between Microsoft, Apple, Linux and BSD… for the same reason that there is a choice between Lenovo, Dell, Compaq, and Packard Bell… for the same reason that there was a choice between Microsoft Office, Smart*Suite, WordPerfect Office, StarOffice, OpenOffice.org… and the last example is instructive because it demonstrates that many will fall by the wayside.
If the 20th Century taught us anything, it’s that markets generally provide a better solution than central planning. (For all that the last few years have shown the limitations of markets, it’s not at the stage that market-fundamentalists have to build walls and erect gun towers to shoot those who try to flee the market economy, in a way that centrally-planned economies had to.)
The beauty of the OpenSource model is that it allows multiple products to be brought out, and compete with each other, in a way that allows far more efficient leverage of the best bits of the losers, and a next generation of everything that incorporates the best of the best (where best means “best for the particular niche that the provider is targetting) rather than meaning “the best for anything.” Or, put another way, it’s a lot easier to build Ubuntu by looking at Debian than it would be for a startup with a few million to build a new Hybrid by looking at a Prius.