You can think of them as the Bitcoin Santas. Every so often, they appear out of nowhere and bestow gifts on people across the globe, a bit like Santa Claus on Christmas Eve. The difference is that they always give bitcoins, the world's most popular digital currency.

Late last year, they came to Yifu Guo. Guo runs Avalon, a company that builds and sells "Bitcoin miners," specialized computers that help run the global open source software system that drives the digital currency.

They didn't tell Guo who they were or where they were from. They merely said they were with an organization called Bitcoin Grant, and they asked him what his plans were for Avalon.

>Whoever they are, they're on a mission to bootstrap not only the Bitcoin world, but all sorts of other open source software projects

Guo was skeptical. There's a website for Bitcoin Grant, but there was no information about who ran the group. There wasn't even a way to contact them through the site. But since the group had reached out to him over email, he went ahead and chatted with them about the future of Avalon, and before too long, they gave him a gift: 10,000 bitcoins, no strings attached. At the time, they were worth more than $100,000, enough to get Guo started on Avalon's next generation of Bitcoin miners.

He says he never did learn who these mysterious benefactors were or why they chose to fund his project. But whoever they are, they're on a mission to bootstrap not only the Bitcoin world, but all sorts of other open source software projects. By definition, open source projects give their software away for free, so they need other ways of funding their hard work, and the shadowy characters behind Bitcoin Grant are dedicated to helping these projects find their feet.

To date, they've mostly funded Bitcoin-related projects, such as Avalon, but they've backed others as well, including Replicant, an alternative to Google's Android mobile operating system, and the idea is to pump money into countless others. "Open source, especially, while righteous in its premise, has long been dogged by financial unsustainability," reads the Bitcoin Grant website. "We want open source to become central to how we move forward instead of being a hobby or an afterthought."

Funding these projects with bitcoins is only natural. Bitcoin is the first open source project with a funding plan rolled right into the source code, and the coders who helped develop the software in its earliest days have gotten rich on the digital currency. You see, when you run a Bitcoin miner, the system gives you bitcoins. We may not know who's behind Bitcoin Grant, but you can bet they picked up their bitcoins before most of the world caught on to Bitcoin.

Tipping has always been a big part of the Bitcoin culture. The digital currency spread in its early days as Bitcoin evangelists simply gave the digital currency to friends and family. And Bitcoiners have been known to hand over tens of thousands of dollars at the sight of a cute sign on television. But Bitcoin Grant seeks to bring a little more purpose to this practice.

They've pumped 25 bitcoins – about $16,700, at today's exchange rate – into a project that seeks to launch a bitcoin miner into outer space. They've funded another that runs vast mining pools for Bitcoin and other digital currencies. And they've backed a new Bitcoin wallet that keeps you from losing bitcoins due to backup problems or computer failure. The Bitcoin Grant website lists eight grant recipients, but we know there have been more.

In March, Mike Hearn got a Bitcoin Grant too. He's a Googler who helps write the peer-to-peer software that runs the Bitcoin network. Though he doesn't remember how many bitcoins they gave him, Hearn says he appreciated the gesture. That said, he thinks Bitcoin will need a more sophisticated funding model to get to the next level of software development.

"It's kind of an interesting model, but it doesn't motivate people to do any particular work," he says of Bitcoin Grant. "To really open the throttle, it needs to be normalized a bit more." For Hearn, "normalization" means things like assurance contracts, where sponsors can use technology embedded into the Bitcoin protocol to jointly pledge and pay for software development.

That's futuristic stuff, so, for the moment, Bitcoin and other open source projects will have to get by on anonymous donations.

After tracking down Bitcoin Grant's top-secret email address, we reached out to them a few times, asking if they'd like to talk about their project. But they haven't responded. All we have to go on is the website – and testimonials from people like Mike Hearn and Yifu Guo.

There seems to be only one basic rule: Don't call them, they'll call you. So if you're running an open source project – whether it involves Bitcoin or not – just keep your head down and keep coding. This Holiday season, you too might get a visit from Bitcoin Santas.