Open Source doesn’t imply the absence of property rights.
It’s a choice to invest my own effort into something I choose to give to some people for free.
It literally requires me to use (at personal risk) my savings to create and give a gift to others.
I don’t see “socialists” risking their own wealth to produce and give gifts to others. They take others wealth and give it to their (usually unproductive) friends.
Big difference.