GNU bash has been maintained by Chet Ramey for decades (although he isn't the original author.) Most of the GNU projects probably count, although some of them have changed maintainers much more often.
R was started by a couple of stats professors, and I'm sure it wasn't their main line of research (as opposed to Lua, Haskell, and OCaml, which are definitely labors of love, but they are somewhat funded, if you consider an academic salary funding).
Julia seems to be a labor of love, although it has had some amount of funding.
Clojure and D both have or had some commercial element, but you can tell it's mainly the love driving it, not the business.
Java and JavaScript are probably the big exceptions, in that they were started by big companies. As well as C and C++, which both originated at Bell Labs.
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And if you are really looking for single person projects, sqlite is probably one of the best examples. If I recall Richard Hipp has actually paid people to work on sqlite occasionally, but he's written almost all the code, and doesn't really accept patches.
Though I'm not really sure if "not accepting patches" like Knuth, Bellard, or Hipp is something to be admired... I have tend to want to control things too, which is probably a bad tendency.