"Marxist" is technically an incorrect term -- there is no State ownership of the property in question, so that nomenclature is inaccurate.
Arguably, "Socialist" might be a more descriptive (though no less pejorative) term, but its still not particularly accurate. While there are elements of economic cooperation (over economic competition), there is no centralized planning -- as in virtually all Socialist States. The freeform nature of OpenSouce is antithetical to Socialism.
The most accurate descriptive term -- and one lacking in moral baggage -- would be "Cooperative." Think of the Harvard Coop, or the Condominium variation called a "Co-op" (at least in NYC), or any other situation where poeple find advantage in the mutually pooling of resources and/or talents.
Open Source / Cooperative Code Development is obviously against the economic and even historic interests of billg and Microsoft. Ever hear an animal yelp when its tail cuts stepped on? Gates' yowling is nothing less; While its barely dangerous to the animal at this moment, its clearly caught his attention.
Makes one wonder, though, how threatened Redmond is by Open Source