Spooner believed that it is beneficial if people are self-employed so that they could enjoy the full fruits of their labor rather than having to share them with an employer. He argued that various forms of government intervention in the free market made it difficult for people to start their own businesses. For one, he believed that laws against high interest rates, or "usury" prevented those with capital from extending credit because they could not be compensated for high risks of not being repaid: "If a man have not capital of his own, upon which to bestow his labor, it is necessary that he be allowed to obtain it on credit. And in order that he may be able to obtain it on credit, it is necessary that he be allowed to contract for such a rate of interest as will induce a man, having surplus capital, to loan it to him; for the capitalist cannot, consistently with natural law, be compelled to loan his capital against his will. All legislative restraints upon the rate of interest, are, therefore, nothing less than arbitrary and tyrannical restraints upon a man’s natural capacity amid natural right to hire capital, upon which to bestow his labor....The effect of usury laws, then, is to give a monopoly of the right of borrowing money, to those few, who can offer the most approved security." [25]
Sure, not as we understand the word "Communist" today.
But there was a time -- lasting decades -- in which words like "anarchist" and "communist" were more-or-less synonymous.
We even find this in Marx himself talking (ironically to our ears) about the "withering away of the state".
So, for many years, "communist" did not mean "big government" but rather the absence of a government needed to enforce laws -- laws of property and contract, for examples.
But more to the point, specifically, Spooner joined the socialist First International, which is summarized here as:
It was founded in 1864 in a workmen's meeting held in Saint Martin's Hall, London.
Its first congress was held in 1866 in Geneva."