A question that has had be quite interested for some time, but one that I could never truly find a satisfactory answer for, was why has FreeBSD been so successful in its proliferation compared to the other BSDs?
My own impression is that FreeBSD is remarkably well architected, throughout the FreeBSD operating system component model -- as in regards to the OS kernel, the FreeBSD base system components, the popular baseline userspace tools, and the broader FreeBSD ports tree. Not as if to flatter, I believe this assertion is well backed of an analysis of the operating system source code, itself.
In a manner of an informal, if not social view: In my own experience, proceeding from an albeit informal experience with Debian GNU/Linux, I think Debian itself has honestly done a lot with regards to end-user support and Debian developer support -- perhaps more to an effect of an emergent popularity, if not ultimately to the ongoing "Variable-Gain Feedback Loops," so to speak, of the Linux developer ecosystem. I do believe Debian is, as an operating system, is more monolithically architected than FreeBSD, but it retains an open access model for contributions -- such as most free/open source software may, certainly, whatever the exacting terms of any single software license may be. As Debian being a popular Linux OS distribution, I believe Debian itself has weathered its popularity very well, over the years.
Perhaps Debian -- in its baseline OS -- might seem to be evolving more than FreeBSD, as in a simple estimate of discussions and subsequent source code changes over time, but FreeBSD is not without analogous changes -- such as in reference to the SystemD adoption in Debian. Assuming "Change is good" -- if one may assume it thus-- I would not want to cast any manner of shadow on the Debian doorstep, so to speak. Across so many effective committee discussions and subsequent changes in the Debian baseline OS, as Debian develops over time, but Debian remains Debian -- formally, a project sponsored by the GNU Foundation and Software in the Public Interest, Inc (SPI).
Contrasted to the Debian revisions and the evolution of the Linux kernel, to my opinion, FreeBSD seems to adopt -- and I think, usefully so -- a philosophy that might seem to be hinted towards as of the idiomatic phrase, "If it ain't broke don't fix it," or some manner of a practical philosophy as with regards to the design of the kernel, itself, and the "User space" features of the FreeBSD operating system. Not only is FreeBSD well architected, I think -- and I have not as yet looked at OpenBSD or NetBSD, candidly -- it's also well documented in its source code -- even in so much as the makefiles of the whole OS toolchain. Also, there's a lot of meaningful documentation in the manual pages, in books published of the FreeBSD Project, and in broader academia -- all the further technical documentation -- veritably as FreeBSD being a "Work of the state of the art."
Not to try to make a till out of any single relative estimates of popularity, or support, or OS-architectural qualities, juxtaposed to Debian, I understand that Debian itself had managed to have picked up some more of a social if not commercial interest with Canonical's projects -- Ubuntu Linux deriving originally as a fork of Debian, with subsequent forks being developed of Ubuntu. Personally, I could wish that FreeBSD would be picked up by Samsung's Tizen developers -- candidly, I think a FreeBSD fork of Tizen could be easily done, as the Tizen projects are quite squarely managed under the Samsung IRIS system -- but I would certainly not want to "Rock the mobile boat," so to speak, neither as if to figuratively or literally remove any jetwash from Linus Torvalds' projects. Myself, I stick to low-flying things.
Though there are certainly a number of forks of FreeBSD, too -- not to be tedious of a manner of a logical assertion that a
fork of a fork, in its source code, is transitively a
fork of the original baseline, however a social identity of a software project may evolve along with the development of the software, and however the original baseline software may be changed in subsequent
direct forks -- thus, that there are quite a few forks deriving originally of FreeBSD if not furthermore influenced of designs, broadly, designs in "Other" BSD operating systems, in the whole BSD development ecosystem -- I don't believe anyone has tried to too radically change the OS. FreeBSD certainly retains a stable design, in its computing architecture.
Although there may be a critique about some of the component models applied in FreeBSD, but software such as the Forth bootloader does not necessarily have a "Shelf life." Though perhaps the Forth language itself might not seem to be one the hippest ones on the Headhunters' "To Go" lists, today -- juxtaposed to HTTP dot CLI and so on -- and perhaps a simple concept of a stack machine may ever seem to go
out of vogue, but theoretically, that doesn't change its component-wise functionality, in applications.
Trends may come and go, enterprises acquired and acquired again, social parties and all the confetti and so on, but so far as the nuts and bolts of it remain essentially unchanged, the OS persists across all the advertising.
Perhaps FreeBSD was designed in such a way as that it is naturally extensible for new applications in new "State of the Art" developments, without any wide-sweeping changes required in its source code. Personally, I haven't been closely following the discussions about microkernel designs in Linux -- I'm certain that there must be someting of an academic ecosystem about it, also, though I can only make a broad estimate of such. I myself am not even informally familiar with the academia about Linux itself -- as much as I am well not a formal part of the Linux developer ecosystem, not in any formal or direct regards.
Personally, though Debian has so much more of packaging support, I think FreeBSD is much more accessible in its essential OS design. I feel that I should be wary of trying to convey too much of a "New sports car" vibe about it, though, candidly -- figuratively, to keep all wheels on the road....