Today I read an article that posited the theory that Apple Computer's time has come and gone as the main Windows competitor and that Linux is the new challenger. That's where the emerging mind share is and where a lot of media attention goes, while Apple only talks about the G4 processor (which they don't make) and funny-colored computers, neither of which is all that innovative.

Now, Linux people are rather zealous, possible more so than Macintosh people. And they've done a lot to capture a certain amount of mindshare for their OS, although I doubt most people know what Linux is. Apple did fund their MkLinux effort to port Linux to the Apple's computers, but Apple dropped that effort a year or so ago (it's still kept in development by the user community).

Apple's next generation OS, MacOS X, is based on the BSD version of Unix. BSD also has an Open Source policy and a strong user community. It's been around longer, meaning that it's members aren't as hotheaded as the Linux crowd. But conversely, it has never taken off the way Linux has.

I read an article about NetBSD, which is a BSD variant aimed at maximum portability throughout all hardware platforms. The two other Open Source BSD variants are FreeBSD, which is aimed at maximum features for the i386 platform, and OpenBSD which is focused on maximum security.

What all three BSDs have is a significantly different licensing policy than the various Linuxes. From what little I understand, Linux's GPL specifies that all source code additions must be made publicly available and free for others to modify. This makes it very hard to make money off of an operating system. You can make money off of the support and some other value-added options, but support is not a big revenue stream when your OS aims for ease of use (like the MacOS).

BSD is also open, but it does not require people who modify it and redistribute it to open their source code. Anybody can take the current NetBSD and sell it (with or without adding or modifying it) for however much they can get a fool to buy free software for. There is a requirement to maintain the credits on the various programs. And if you want your code to make it into the main distribution you have to open it up.

This means that there are several commercial BSD solutions, such as Tenon's MachTen which runs on top of the MacOS, or BSDI for the i386 platform. This is a better solution for Apple, which can now take a robust OS and add their own specific code without having to make their code open source.

There were other reasons for Apple to base MacOS X on BSD. NeXTStep was also based on BSD, and all the engineers that Apple aquired from NeXT had all that BSD experience. For these reasons, Apple made a good choice in basing their new OS on BSD and not Linux (or a couple of other candidates).

Note that only recently has Berkeley decided to drop a clause in the BSD licensing requiring derivatives to credit UC Berkeley for the original BSD implementations. Apparently this was some sort of problem, although I can't imagine why.