I seem to recall a profile of the game and it's creators that said it's mostly by choice.
Found it: they were offered 300K just to license the name.
He has refused a programming job at a major developer
(he asked that I keep its name off the record) and
turned down a $300,000 offer from another company to
license the Dwarf Fortress name, fearing that the
proposed sum wouldn’t sufficiently offset the long-term
donations drop that would likely result.
A one-off 300K isn't a lot for two people to live on if it would cut off their donation stream completely, and if you've been doing this for 10 years it may not be easy to find a job.
There are still a lot of employers who see time spent on your own venture as a gap in employment history. I mean, I guess it literally is, since you aren't an "employee". But they completely discount any applicable experience during that time.
The founder Tarn Adams has a Ph.D. in Mathematics from Stanford, so I don't think any of his potential employers will mind that he spent his time working on a fantasy economic simulator of this scope.
I think it's indicative of the value of the property that just the name alone is worth 300K. If they were interested in commercializing the game I suspect they would be able to make a lot more.
They could almost certainly make a lot more money if they were willing to compromise even a little in the direction of usability.
They aren't, though, so they're making a conscious decision to forgo that money in order to keep their vision (as maddeningly abstruse as it is) intact. In that respect Dwarf Fortress is a lot more like an art project than a commercial game.
For a comparison, Gnomoria (http://gnomoria.com), which is an unapologetic DF clone but with basic graphics and first-party modding support, sells for $8 a pop on Steam and has 2,000 reviews despite still being in "Early Access" status.
I can't find a reference right now, but I believe Toady has turned down large offerings from Notch, among others. He seems to believe that too much money would take away from what he's doing.
I think it's best to think of Toady like a crazy man building a cathedral down the road, single-handedly, using only tools he made himself. We can only sit and watch in awe and appreciation as the cathedral takes shape. And support him on Patreon, I suppose. :)
That's roughly first year school teacher income level, or parish priest stipend level. I think Tarn was a grad student before he got his doctorate, and $2500 would not be a pay cut; assuming that grad students loved their field at least once upon a time.
Per capita median personal income in the USA is right around that level, so 50% of the population earns less, while being statistically unlikely to love their job. If half the country hates their lower paying job, they have little to complain about in a relative sense.
