It lists many reasons why I don't open source my side projects.
Open sourcing is meanigless without considerable additional work in form of quality assurance, documentation, project management, marketing.
As a developer you should weight whether it is worth the cost for the return of exactly what? Getting your stuff out there? Developer street credits? Maybe a consulting gig down the road?
Or is your time better spent doing other things?
For example, in the early '90s I wrote a tool to pull a small newsfeed from an NNTP server. I called this tool "suck". It was written entirely for myself.
When I finished adding new features that I had not realized initially that I needed, and finished fixing all the bugs that I new about, and had used it for a while without encountering any new problems or discovering any new features I wanted, I made the documentation presentable, made a tar ball of the source and documentation, put it on my public FTP space at the University of Washington, and made a single post to usenet announcing its availability and location, stating that it was public domain, and stating that it did everything I wanted and I'm not going to be doing any further work on it and would not be doing bug fixes or enhancements unless they were fixes or enhancements I needed.
So aside from the small time spent cleaning up the documentation and putting it up on the FTP server and writing that one announcement post, open sourcing it took no time of mine.
A year later I had some enhancements I wanted. I made them, and then like last time I put it all in a tar ball and put it up for FTP. I then went to usenet to post an announcement that suck2 was now available, on the same terms as suck, and to my surprise I found that someone else had just announced suck2.
They had found suck, and it did much of what they were looking for, and had used it as a starting point to make the tool that they wanted. They were actively maintaining and developing their suck. I kept using my suck2, since it did exactly what I wanted, but from then on if I had occasion to recommend pull feed software I recommended the other suck2.
Their suck made it into several Linux distributions. By then they had changed enough that I doubt there was any code of mine left, but it was still cool to see something that had started from something of mine there.
As long as your side projects aren't in a state that could harm someone who tried them, why not release them? Just make it clear and prominent what level of post-release interest you have (and "none at all, including ignoring all communications about this project" is fine).
I don't know how much clean-up id did on doom's source before releasing it, but my understanding is that they didn't do that much. And I wouldn't be playing Doom today if it weren't for that source dump.
I'm not playing dwarf fortress. I kinda would like to, though.
Tiny, obscure project but it was just what we needed, after a few fixes for our use cases.
The thing is simply: it is easier, cheaper and less risky to make the code open than keeping it closed on my home machine or in paid private repositories.