dbus is also a dependency though. If you are on the bus (heh) that says systemd is a hard dependency that should be avoided then dbus is also the same thing.
I agree with your logical consistency, but I'm curious: is D-Bus sufficiently specified that one could write an alternative to it? That is, is it a hard dependency or is it itself an interface? I'm not nearly sufficiently experienced with desktop Linux application development to know. ;)
Yes, DBUS is specified [1]. There are multiple implementations shipping (dbus reference implementation and dbus-broker), as well as several different client libraries.
As dbus user, or application, you just need some client library. As an operating system, you also need a daemon running, which is routing the messages among all the clients.
IIRC at least part of the reason for sd-bus is the need for using D-Bus between parts of systemd during early boot when "normal" D-Bus is not yet up and running.
FreeBSD developers are actually looking at something like systemd themselves. The fact that systemd itself doesn't run on it is just the consequence of POSIX being inadequate for its implementation, since it relies on a bunch of Linux specific features, like cgroups etc.
I am personally in the camp that doesn't mind that, Linux users should get the best possible software given their system capabilities, not the lowest common denominator one just for the sake of it. (Free)BSD developers are also not looking to make sure their stuff works with Linux, which I think it's a valid approach.
GNOME itself does exist on the BSDs, by the way knocking down the argument of systemd being a hard dependency of GNOME along the way.
> FreeBSD developers are actually looking at something like systemd themselves
If this claim were true it still is beside the point of my comment, that systemd itself has a "Linux only, and we don't care" approach, and dbus for the moment is not that.
> GNOME itself does exist on the BSDs
Yes the ports tree is a wonderful place for those things to sit for those who are interested and for a larger portion to not bother installing them. I don't know how many patches they applied to get it working or what the cost and effect of those patches may be over time.
