I don't think what happens in open source software is accurately described as "communism" in any sense of that word. Especially considering that OSS in practice is a scheme for corporations (including those in direct competition with each other) to pool resources and share their research and development costs.
I agree with your comment. We have to keep in mind that "communism" is a word for utopian society (e.g. no state, no "money", no classes, and common ownership over the means of production) which is the end goal of "socialists" stemming from "Marxism" which is a socio-economic analysis of class relations. The core of "socialism" is the question about ownership of the means of production (as explained by Marx).
The chief reason for why free and open source software isn't "communism" in any sense of the package of things that word contains is that in practise it almost always leads to a very controlled extreme planned centralised collectivist systems. Free and open software development and communities on the other hand are based on extremely individualistic non-centralised non-planned and non-governed system.
If free and open software was inherently "Communist" or "Marxist", then we'd have "ONE FREE OS, ONE FREE DESKTOP, AND ONE FREE DESIGN". Instead we have several free software operating systems, dozens of competing desktop environments, and uncountable number of designs for every individual taste. If you want to know more about this point of view, I recommend you read the "Road to Serfdom" by Friedrich von Hayek.
It's true that in free and open source software we people share the code and tools (i.e. the means of production) to some degree. However we people still inherently govern the domains of our work and we get rewarded for the work that gets done. Instead of "money", hackers often get rewarded e.g. by "fame". Eric S. Raymond explains quite well in his book Cathedral and the Bazaar how this works and in great detail too.
But most importantly there is no central planner which would dictate how things work and coordinate the operations. If some guy doesn't like how a free and open software project is being developed, he can fork the fuck out of it and create a competing project. And this makes it sound more like anarcho-capitalism than anything else. We don't have "centralised state" that would set the framework where code is allowed to happen and "market of ideas" operates. This fits into agenda of our current corporatist society quite well and even companies which are in direct competition can benefit from it pouring resources to projects of mutual interest.
It's true that when we inspect how free and open software projects are developed, we at times counter cases of central-planner but often we notice that this entity is restricted by the pressure from the users and the fear of having project forked and lost "fame" / "reputation". This is basically why "dictators" that lead their projects aren't sole rulers of their domains. Most commonly we see governing bodies of few selected individuals aka. oligarchies that manage the free and open software project.