"libertarian" in that context appears to mean having everything controlled by a democratic government to which everyone voluntarily submits.

?! I gotta see this!

Oh, wait, nevermind:

Anti-authoritarian, anti-propertarian varieties of left-wing politics, and in particular of the socialist movement.

Libertarian socialism is the anti-state tradition of socialism.

The version of left-libertarianism defended by contemporary theorists like Vallentyne, Steiner, Otsuka, van Parijs, and Ellerman features a strong commitment to personal liberty—embracing the libertarian premise that each person possesses a natural right of self-ownership—and an egalitarian view of natural resources, holding that it is illegitimate for anyone to claim private ownership of resources to the detriment of others.[17] On this view, unappropriated natural resources are either unowned or owned in common, believing that private appropriation is only legitimate if everyone can appropriate an equal amount, or if private appropriation is taxed to compensate those who are excluded from natural resources. This position is articulated in self-conscious contrast to the position of other libertarians who argue for a (characteristically labor-based) right to appropriate unequal parts of the external world, such as land

Arguing that vast disparities in wealth and social influence result from the use of force, and especially state power, to steal and engross land and acquire and maintain special privileges, members of this school typically urge the abolition of the state. They judge that, in a stateless society, the kinds of privileges secured by the state will be absent, and injustices perpetrated or tolerated by the state can be rectified. Thus, they conclude that, with state interference eliminated, it will be possible to achieve “socialist ends by market means.”

I think you may have misunderstood the way "socialist" was being used there.