FreeBSD has been released in 1993 and has been a well known OS in the hosting world.

Erlang has been released in 1986 and has been a well known language for message systems.

When I think about exotic I think about some new tech that sound really nice but is still very unproven.

JavaScript is from 1996, it's 25 years old, and apps built with it are used by billions. With regards to the backend, it has a vibrant full stack ecosystem, it's performant, simple, and easy to hire talent for.

It's okay not to enjoy JavaScript (I'd always prefer to go with Dart or Rust myself), it's okay thinking that other languages (and ecosystems) are better equipped to solve some problems, but calling it unproven and exotic is very surprising to me.

FreeBSD was a more stable/mature platform to build on when WhatsApp was designed, particularly in terms of network performance.

Is the implication that FreeBSD is less mature now, intended? I'm assuming not. The BSDs have grown in popularity significantly in the last couple years.

No, but there are signs of distress, IMO. I think their decline in usage has resulted in a decline in port maintainers, which is a bigger deal now that systemd is the default on Linux for so many things.

In the 32 bit days it wasn’t hard to get most Linux binaries to run, now it’s virtually impossible for an end user to do on their own.

Pretty much nothing important depends on systemd, for the simple reason that it’s proprietary and non-portable. Thus, even if there is some code that depends on it, it’s optional.

Also, Linux binary compatibility - the capability to run unmodified Linux binaries - works much better now than ever before.

> The BSDs have grown in popularity significantly in the last couple years.

Is the market share for BSDs growing?

Which market? If you take eg gaming consoles, then FreeBSD maintains steady 1/3 of the whole market, compared to Linux 0%.

Has the PlayStation market share grown in the last couple years? Also, Linux is probably going to grow when the Steam Deck is released.

Even if the PlayStation is growing, I am not aware of BSD growing in desktop, server, embedded devices, etc.

Linux isn’t growing in those markets either. Moreover, it’s increasingly seen as a liability - thus increasing efforts to replace it with eg Fuchsia.