What about those who opt not to use Linux?
Relying on a Linux only init service is pretty much a middle finger to the users of that software on those platforms.
Then your not going to be able to use Gnome 3. Personally, I'd rather they use advanced features even if they're Linux only. I'm sick of Linux being held back by some misguided notion that every application needs to be ran on a version of NetBSD from 10 years ago.
There's an effort to bring these features to OpenRC which works on Linux and FreeBSD, but the Gnome developers have shown absolutely no interest in assisting the project, even though they'll be limiting their own share of the desktop environment space.
I think it's important to have a standard API going forward rather than porting to ten different APIs. We'd be more than happy to support OpenRC if you implemented the logind APIs we require.
An API doesn't have a license. It is just the code which has a license. Do you mean you want to copy the code to reuse it under OpenRC, or are you really talking about the API?
Regarding API license: Just ask systemd mailing list. They will tell you that API doesn't have a license, only the code.
Gentoo GNOME packagers decided they'd make GNOME in Gentoo depend on systemd. I don't see why you expect GNOME developers to help out with another init systemd. That should be up to init system developers. Just implement the same API and/or ensure the API is fixed so it can be implemented across init systems.