What for the discussion is the subject? The notion of what a 'libertarian' is in contemporary or historical sense, or the logical demonstration of knowledge of 'free will'.
I would also struggle to find an instrumental definition of the use of the term 'free will' when interspersed with the notion of a 'libertarian'.
Is the author of the question asking if a 'libertarian' has a principled and dogmatic duty to a cause or number of causes?
If so you would need to find a present day 'libertarian' of the political activist variety who has stood for elections and enquire with he or she what causes and beliefs are held.
If you mean the type of 'libertarian' you find in online forums who appear to have some cultish fetish for the iconic authors of certain works on economy, again you would be obliged to find out if the mindset of such a person was causally dogmatic in servitude to a creed of ideas and principles.
Again if you found such a person politically campaigning or making public speeches you might
enquire as to how their thought process to common issues of society and governance would
effect remedy. If such a person could not adapt to your scenarios and they, given all reasonable
time to respond, can only reel off tracts from cult texts then the extent to which they are reliant on them as the source of answers, it may reveal how much of their present action is determined by idealism or ideological creed.
It would also rather depend whether being a 'libertarian' only meant signing up to preach its creed.
Much as a PR person knows they are performing a duty of their job.
And how much can be said of the person committed to their job that they either have the mindedness to form new opinions or act on new beliefs formed from those opinions?
If there is the matter of acts of 'determinism' then it is at the level of conscious processing of
new information. The subject in its ontological universe may be committed to being an
authority in 'libertarian' ways as much as the rightness of action he or she finds concreteness in
situational ego.
Does the subject have 'free will'. On an individual basis without claiming anthropological certainty,
having decided their class of person. The answer lies in the extent you could engage in participatory conversation and to what extent the synthesis of new conceptual arrangement modify the hierarchy
of beliefs in terms that were posited as the creed of the person. In other words whether the ideas
or solutions a 'libertarian' posits as terms or remedies in economics have been taken on purely as ideas
or as a succession of interpenetrating factors and causes with precedence that allow plausible
determination in there operations. And that they can be elucidated as such.
Or alternatively such a person may be socially committed to the social creed of the matter and
no inquiry would yield self evident understanding of the formulation of the ideas held.
Whether randomness is the consequent of the alternative to determinism by understanding, that is
another point of inquiry. That when an ideologically primed individual is challenged to reveal the
concepts that bring about the understanding, again perhaps challenged to solve an analogue of
the same problem, there is the problem of the subjective will.
Since creativity is a subjective expression, the fact that there is this apparent difference between
the observer and the observed, that free will can only be simply a matter of constraint has more
tractable ground in reality. You might therefore wonder whether the lack of engagement in
self agency with notions in novelty are for the presence of a constraint which could be external
social pressure, in the form of power hierarchies or individual in the form of instinctual disposition to
the making of new ideas which in play run against an established mode of being and mindset.
Freedom it can be said is limited by partiality, which has a number of causes including an establish
identity of the subject as a subject historically socially conditioned.
I don't want to seem confused, but 'rational free will' and its absence is not a marker for constraint in my opinion, since ideas alone have operational efficiency from unconscious sources in the brain. I think we sometimes refer to those as gestalt or unconscious picture thinking, and for the subject's universe are its own determinations and options for courses of action in its own process of determinate willing.