I've done a few open source things, mostly bugfixes or minor enhancements. Most of those I was being paid by my employer for, and it was either something I wanted available more widely and it was worth going through the process or it was a pain to manage patches so it saved me time to get it accepted upstream.

Either way, I don't get paid a royalty for work for hire from my past employers, so I don't expect a royalty from anyone else. And I've not worked on a project basis either; so I'm getting paid for having my butt in the seat and anything that happens afterwards is a happy accident.

I've open sourced some personal stuff too, although I don't know that anyone has looked at it. That stuff is usually more like nobody should need to write this again. Not much commercial market for a PPPoE client that can handoff to a standby machine anyway, but maybe it will be useful for someone, some day.

I've got another project in the works, but it's mostly a bit of glue around other people's open source code. If I wasn't retired, I'd try to get an employer to pay me to write it (and it would get done faster!), but I can't see why anyone would pay for just the software. Consulting on the software, sure; but then again, if you were to rely on it, you'd probably want to cultivate in-house expertise to reduce dependency on outside help.