Your premise is false: Open source software has nothing to do with communism, Marxism or socialism.

How many successful open source software created in communist countries do you know? Isn't it surprising that most successful open source software have been developed in capitalist countries ?

In fact, only capitalist countries give you enough wealth to spend a lot of time on hobbies, like developing open source software. If you were living in a communist country, you would probably spend most of your time searching for food.