I've got one data point for you, though I don't think you can guesstimate income based merely on one factor, especially not github stars (we only have 295).
My company is based on Open Source software (Webmin, Virtualmin, Cloudmin, and Usermin), and it sounds sort of similar to your situation. When we started the company based on this stuff we had several major companies in our target market (and we chose our target market, and chose to focus on Virtualmin rather than other features of Webmin, because that market already knew us and used our software in visible ways) using at least one of our projects, almost a million downloads a year, and my co-founder and I had both been making a decent living doing contract work based on it and writing about it.
Today, Webmin has about 1 million installations worldwide (and has grown to ~3.5 million downloads per year). We make enough money from our small proprietary extensions to Virtualmin and Cloudmin to support three modest salaries. It is not $100k/year for any of the three people working on it, though it's not an outrageous dream to think we could get there..we've had much better years than we're having this year or last year, however, so revenue is not necessarily growing like gangbusters, despite our userbase roughly tripling in the time the company has existed and still growing at a comfortable clip annually. Ours is sort of an open core model, though the core is very large (~500kloc) and the proprietary bits are very small (~20kloc), which may be part of our revenue problem.
I think there are some things you're probably underestimating (not to say it should discourage you, I'm just trying to open your eyes to some challenges you will face that you might not expect):
When you sell Open Source software, support is your biggest value add, even if you don't want to be a support company. Support costs a lot of time and money to do well. Time and money has to be balanced between making things better and supporting existing users on the current version (true of proprietary as well, but proprietary vendors don't have a million people using the free version and expecting help). Growing the free user base (which can be a side effect of having people working full-time on it) can paradoxically lead to less time and money for making the software better. We fight this battle all the time. To make our current customers and OSS users exceedingly happy with our level of support is to severely limit our ability to deliver next generation solutions. We run on such a shoe-string, and compete with such huge players, that it's always a struggle to deliver both (and we fail plenty).
So, plan to hire someone to help you support the software, eventually. If we were comfortable leaving our forums to "the community" and not bothering to have an official company voice present every day helping answer the hard questions, we could increase our own salaries by a lot (we pay our support guy more than we pay ourselves), but I don't know that we'd continue to see the growth we've seen in our user base, which we also value. We make things because we want them to be used, not just because we want to make money.
Get used to having demands thrown at you every day. The level of documentation and completeness and rapidity of development expected of a product is vastly different than that of an Open Source project, or at least the way you have to respond to it is different...even for users of the Open Source versions. We have over 1,000 printed pages worth of documentation, plus a couple hundred pages of online help, and still get complaints about our documentation regularly. And, we have more "features" than any other product in our space, including the two big proprietary competitors, and yet still get feature requests all the time (and it's harder to say no than to just implement it, which can hurt usability). A million users generates a lot of feedback. It's a very high volume of demands to answer to. Ignoring them pisses people off, saying no pisses people off, and saying yes often risks making the product worse or more complex for the average user, hurting long-term growth. Even saying, "Not right now" pisses people off. You're going to piss a lot of people off, even if you're just trying to make the best software you can and make a decent living.
I think what I'm trying to say is, think about it for a while before committing to your plans. If you currently have steady income, hang on to it while you sort out a few details.
Try to firm up what your users would pay for your value add. Try to figure out how many of your users would pay for your value add. The only sure way to do this is to actually have users pay you something for your value add.
Try to figure out how you will automate support (hint: You can't, because automated support almost always sucks; even Google has awful automated support, and they're good at almost everything.) At least figure out how you will streamline it and offload it; have an active forum already? If not, get one. Have a community of people talking about your software already? Get one. If Open Source based business were a Pokemon, community would be its special ability. So, you should start cultivating that now, even before money is coming in.