Earlier quoted context omitted.
There's no general answer to your question. It's like game theory, depends on the players and context (technical, legal, financial, market maturity). Juce and PyQt were created by single developers, so it's not impossible. Staking out and defending a niche would be a prerequisite, open-source or proprietary.
Is there a list of specific answers? I don't even know of all the ways one could organize a project. I suspect that might generally be the case for a lot of people, too. Publishing and promoting a project is a completely different skill set from developing it. It feels like the majority of developers default to thinking of "release open source" or even just "release" as meaning "publish on Github with the MIT license…
"Open" is as much a state of mind and development practices as it is a license. JIRA shipped with full source code while remaining proprietary. This removed customer concerns about JIRA going out of business, no need for source escrow. Customers ended up making modifications to the source, which then influenced the Atlassian roadmap. Conversely, one can have an open-source license, but a dev culture that rejects external input, e.g. Calibre. If a vendor focuses on business goals first, then creates a culture to support those goals, license choices will become clearer.
There are useful history lessons among these links:
1) Free Software Business mailing list archives (1993 to early 2000s), http://www.crynwr.com/cgi-bin/ezmlm-cgi?iis:0:201311#b
2) Self-publishing docs+screencasts with 90% royalties, earned railstutorial over six figures in a market where most technical books are lucky to earn $10K. Relevant to OSS biz models: https://news.ycombinator.com/item?id=7350265 & screencast toolchain: https://news.ycombinator.com/item?id=8932387
3) Bootstrapping 101, http://discuss.bootstrapped.fm/ & http://www.startupsfortherestofus.com/
4) ISV (Stardock) 2014 report, http://www.stardock.com/press/CustomerReports/Stardock2014.p...
Resources on business models:
5) The Business Model: Theoretical Roots, Recent Developments, Future Research, 2010, https://noppa.aalto.fi/noppa/kurssi/23e21090/luennot/23E2109...
6) Free Software and OSS Business Models, 2008, http://www.springer.com/cda/content/document/cda_downloaddoc...
7) Any good book on organized crime / unregulated business. Boundary conditions inform risk management, i.e. early recognition of failure scenarios to be avoided.