I'm not a fan of government-enforced socialism or communism. But if you can get enough people together to willingly participate independently, I'm chill with it. And FOSS software is an example of it working out alright.
That's not the definition of socialism at all.
If you think about it, it's actually much closer to the principle of right-wing Christian charity rather than the left-wing sharing of means of production.
Many in the US tend to associate Christianity with right-wing ideology, but there's actually quite a few examples of a varied history of left-wing Christian thought and action. Sticking to US history: Reverend Martin Luther King, Jimmy Carter, Dorothy Day (https://en.wikipedia.org/wiki/Dorothy_Day). Outside of the US, Liberation Theology in Latin America was an ideology/movement explicitly linking Christian (mostly Catholic) teachings with Marxist-inspired struggles for workers' rights (sometimes those links are easy to do, if you focus on quotes such as "blessed are the poor").
I do agree that FOS software is not socialism, and that donations aren't socialism. But it's important to note that many people who work on FOS software do so without expecting anything in return. I think that idea is in sharp contrast with typical right-wing and centrist economic theories that view human beings as mostly money-driven, self-centered individuals.
Did you mean right-wing ideology? (Calling @tptacek and @patio11 ....)
Pretty sure Jesus never said anything about the forced redistribution of wealth against your will being good.
Jesus actually did have a pretty clear statement in favor of taxes, the most common form of forced redistribution of wealth. https://en.wikipedia.org/wiki/Render_unto_Caesar
on that usage then i think the proper wording for "the opposite of capitalism" would be something like non-capitalist (or even anti-capitalist maybe?)
(apologies for the depression)