Comment 1 for bug 1469819

QtUbuntu only tries to connect to dbus when app requests contents of the clipboard for the first time, and not at startup.

Testing a simple QML file with qtubuntu, it works fine without a dbus service running.

If application does this at startup, qtubuntu may be a source of a crash, quoting the relevant code:

void UbuntuClipboard::setupDBus()
{
    QDBusConnection dbusConnection = QDBusConnection::sessionBus();

    bool ok = dbusConnection.connect(
            "com.canonical.QtMir",
            "/com/canonical/QtMir/Clipboard",
            "com.canonical.QtMir.Clipboard",
            "ContentsChanged",
            this, SLOT(updateMimeData(QByteArray)));
    if (!ok) {
        qCritical("UbuntuClipboard - Failed to connect to ContentsChanged signal form the D-Bus system clipboard.");
    }

    mDBusClipboard = new QDBusInterface("com.canonical.QtMir",
            "/com/canonical/QtMir/Clipboard",
            "com.canonical.QtMir.Clipboard",
            dbusConnection);

    mDBusSetupDone = true;
}

Will consider that as an enhancement.