This "family" of distributions has been the most popular over quite a few years, but has seen a parade of vendors come and go, and all appear to be heading into business models involving a lesser degree of releasing the collections of software as "free software".
Red Hat Linux was the replacement (at least in mindshare) to Slackware . It was notable for its use of the installation tool RPM that is a fair bit more powerful than Slackware's pkgtool installation utility. RPM provides a relatively robust system for installing, de-installing, and upgrading "packages."
Slackware provides a few installation features that RedHat doesn't, notably installation assistance with the UMSDOS system (installing on a "live" MS-DOS file system, with no need to repartition drives or create ext2 file systems).
RedHat has a major advantage over distributions such as Slackware in that there is direct support for a number of non-IA-32 architectures that have included Alpha, Sun SPARC, PowerPC, amongst others.
In the interests of providing some better graphical tools, they founded the RHAD - Red Hat Advanced Development Laboratories, where they are working to produce further GUIed tools in conjunction with the GNOME Project.
Red Hat Linux is being discontinued; come 2004, you will have to choose between either:
Commercial releases such as RHAS (Red Hat Advanced Server), priced at levels from hundreds of dollars per CPU to thousands of dollars per CPU, or
Which is a "community-sponsored" distribution available freely.
This project distributes community-usable releases of "Enterprise Linux" distributions based on Red Hat Enterprise 2.1 AS and 3 ES.
It appears likely that this will be the end of Red Hat Linux as we have known it.
With the great popularity of Red Hat's collection of "Linux software," many have built distributions that are more or less derivative of it, all using the RPM package management tool.
It seems commonly regarded as opening hostilities in a "war" against Red Hat.
This started as a "clone" of Red Hat Linux, being "99% compatible," with various patches and package improvements.
They went through some significant financial difficulties; their business model is now loosely that of a "club;" if you want early access to new versions of the distribution, you need to pay a $66USD/yr "membership fee" to gain access to this.
Yet another RPM -based Linux distribution. Primarily notable for offering a PowerPC version, they were also amongst the first providing System 390 support.
Their other "claim to fame" was their clustering Server Edition that supports SMP and provides some "failover" capabilities.
At one point, they were trying to generate riches by doing an IPO; that fell through shortly before the tech stock market fell apart in 2001. They have since decided to specialize in supporting Asian markets, and the company stock is now traded on the Osaka Stock Exchange.
Caldera/SCO are a set of "litigious bastards." They were formerly somewhat related to Novell, and their systems tended to include support for Novell LAN services.
Notice that all of these products have since pretty much disappeared from the market. Apparently their efforts didn't help very much
They also carry a product called Caldera OpenDOS, which used to be known assortedly as DR-DOS and Novell DOS 7.
This actually points us to where their actual source of sales seems to be, namely in suing large vendors. They bought out DRI, and then (successfully) sued Microsoft for its anticompetitive behaviour with respect to Windows 3.1.
In 2003, the " big news" was that Caldera bought out SCO , and have threatened IBM on the basis of the claim that IBM has included proprietary SCO code in versions of Linux. There have been some rash claims about ownership of copyright and trademarks for UNIX, as well as attempts to demand that Linux users pay them around $1500 per host to have access to binary-only versions of Linux.
They have initiated court action against a number of companies including IBM, Daimler-Chrysler, Novell, and Autozone, but despite plenty of filings, they have not identified any intellectual property belonging to them in Linux. See Groklaw for more details on the legal action.
To say that this has caused consternation and anger against Caldera/SCO would be a gross understatement. "Litigious bastards."
www.linux-kheops.com Linux-Kheops - French Linux vendor