Story here, referencing this blog.
It was quite hard to find an actual claim in this article: there is no single piece of text that seems to be something we can evaluate in terms of facts. The nearest is this statement:
"It is, by this stage, becoming clearer that Jeff Waugh’s promise was not trustworthy. GNOME is apparently becoming Mono-dependent, which is a shame."
But the implication is pretty clear; GNOME is now, or soon, dependent on Mono. The source is a bit better, though, it says:
"[T]he GNOME guys want not only to replace libdbus with ndesk-dbus, but they want to nail down everything so that the new ndesk-dbus/Mono bindings are used in as much as possible!"
This is about, then, the acceptance of of ndesk-dbus into the GNOME external dependency set, which is an entirely managed DBUS implementation. The main point missed by the authors of the posts is that there already was a DBUS binding - it was buggy and unreliable, but this isn't about replacing libdbus itself, but replacing the C# binding to libdbus with a managed DBUS implementation. Fundamentally, we're talking about C# apps losing a non-managed dependency, not GNOME gaining a managed dependency. Specifically, it's not about replacing libdus.
More widely speaking though, the fact that it makes it into the external dependency list doesn't make it a GNOME dependency per se - the original decision on Mono/Gtk# hasn't changed, it's allowable as a desktop module. The addition of an external dependency is only of interest to those Gtk# apps in that module set anyway - those are still removable, and thus that external dependency is removable.