It's not communism at all - exactly the opposite in fact. What we have now is far far closer to communist - which by definition is a centrally managed economy (in this case the manager is Microsoft rather than a government, but in practice it differs only in that Microsoft is slightly more responsive) - than any open source proposal.
Open source is a libertarian/free-market approach, not a liberal one. Microsoft is far more useful to the political left than open source would be, it provides a platform for dictating to individual users, whereas open source would give the users as many choices as a free market would give them.
Communism is one of those Big Lies (a certain religion of peace, better described as the religion of blowing heathens to pieces, comes to mind as another such Big Lie.)
Open Source work may well resemble in some ways what communism claims to be, but it is nothing like what communism is.
Communism is an excuse for tyranny, by another name. And indeed, as you state, Open Source is quite the opposite.
Communism claims to be "people working for the common good in an enlightened world", which is not that far from what Open Source work actually is.
Sensible comparisons with Big Lies are senseless.