Anyone reading the works of a European anarchist will see that the word “voluntary” gets used a lot. The term has a different application to that of modern US Libterarian Party types and most ancaps. That’s why a schism has developed.
While the European anarchist tradition also mentions “consent”, it has never linked “consent” with “voluntary”. It perceives these as two entirely different concepts.
In the European tradition “voluntarily” means “wants to” in the most positive sense. It means that the person has decided to do something, because all things being equal, they really want to.
In the European tradition “consent” is perceived as “has agreed to” in the most negative sense. It means that someone has opted to accommodate something even though, all things being equal, they might rather not. “Consenting” is going along with something rather than the fulfilment of a desire. It simply means that someone won’t stand in the way of something.
Voluntarily = desires
Consents = accommodates
In the European tradition, the concept of consent is most usually applied to the process of consensus democracy. This process agrees a consensus point. If a motion achieves enough support to reach the consensus point, then everyone has consented to it, even those who abstained. The purpose of consent in this context is simply to enable stuff to het done, even where some people may have reservations. Anyone can of course raise the consensus point, but only between the question being agreed and the debate starting.
In the European tradition a voluntary association never necessitates a contract. It’s something that people are engaging in because they want to. They got together because they wanted to, and they stayed together because they wanted to. There is nothing else binding them other than the desire to continue that association.
The modern US/libertarian/Rothbardian/Friedman tradition that encompasses most of anarcho-capitalism puts a very different spin on this by defining “voluntary” as anything that is “consented” to. In this tradition voluntary associations are usually bound by contractual obligations.
I’m not here to argue about which definition of the word “voluntary” is accurate. The point that I’m making is that the latter definition is not not consistent with an ethos of freedom. It’s cynical and turns anarchism into a game of “gotcha”. Therefore although I’d consider myself a voluntaryist in the original sense, I absolutely do not consider myself one in the more cynical US Libertarian sense. As far as the Objectivist sense goes, my jury is still out on that one.