It has 2 steady income streams:
1. Monthly sponsorship donations.
2. Forging rewards from the Lisk blockchain. Those rewards are shared with the community.
SocketCluster powers Lisk's P2P network and protocol so on that basis I was voted into a forging position on the Lisk blockchain.
These two sources of income have been just enough to support myself and a couple of casual contributors. Took 7 years to get to this point.
Also, I occasionally did consulting in the past but that has not been reliable.
My experience makes me optimistic about blockchain tech's ability to help monetize open source projects. I'm particularly optimistic about the DPoS (Delegated Proof of Stake) mechanism because it allows big token holders to vote for open source project maintainers to be delegates on their blockchain and allows those open source maintainers to earn block rewards.
Forging on DPoS is like like Bitcoin mining, but a lot less hassle and requires no capital if you can get the votes. I'm working on the Lisk ecosystem now.
Helping others to monetize their open source projects in such a way that they can retain independence from corporate or government influence is my life's mission. My project is just a proof of concept.
BTW feel free to look for my email address on GitHub and get in touch with me if you want to participate somehow. I can't guarantee anything but I feel that the technology and incentives are improving - I'm working on a DEX ecosystem right now which should facilitate this.