I don't want to argue your point and you should read heavily into the "tragedy of the commons" problem that plagues many open source communities, but companies can give back in many ways, in terms of bug fixes, features and improvements to the projects they use (at least wise companies do).
The standard way society compensates persons for useful goods and services is by exchanging currency, not by bartering favors or by saying "look! we made a billion dollars using your software, here, have these free 40 lines of code as a bug fix. thx."
The standard way people indicate to society that they would like to exchange currency is by setting a price for their product.
It doesn't seem particularly fair to say "here world, use my open source project for free," and then get mad that people use it for free.
And in fact, I don't think antirez is saying that. It looks to me like other people, who didn't build Redis in the first place, are the ones saying that.
Open source software succeeds because there's no friction for trying new things. So, initial cost will always be zero. People love seeing their software used for new things, so nobody wants to prevent adoption. At the same time, nobody wants to support billion dollar companies for free. It's a perverse inversion of incentives.
Redis gets feature requests from companies all the time (implement X! It'll save us from lots of complexity and internal support time!), but they don't want to pay for it. Redis also gets support requests from big companies (where employees have already exited or sold stock back or are out buying Teslas), and I get to answer their questions for free too. I'm really happy Redis is running your multibillion dollar company and I'm certainly happy you see no irony in asking for free support when your company is visibly hemorrhaging idle cash. Sometimes you just have to say http://www.urbandictionary.com/define.php?term=fupm&defid=54....
ideally, what you want to say is "here's my software; if you need a good, free solution you're welcome to use it. however, if you're making millions off a stack that my work is essential to, i would like a share".
cory doctorow has made a similar argument about copyright and the absurdity of one-size-fits-all:
> We're trying to retrofit the rules that governed multi-stage rocket ships (huge publishing conglomerates) to cover the activity of pedestrians (people who post quotes from books on their personal blogs). And the pedestrians aren't buying it: they hear that they need a law degree to safely quote from their favourite TV show and they assume that the system is irredeemably broken and not worth attending to at all.
In Twitter's case, we've also contributed to the Redis ecosystem via twemproxy: https://github.com/twitter/twemproxy
Twemproxy helps scale some of the traffic for the top websites in the world: https://github.com/twitter/twemproxy#users