I've decided to retire the directory today. The excellent new medusae.space directory by Mjollna & Laërte is growing at quite a pace, and will easily outpace my efforts. Their DB backed approach also has some advantages for nesting, multi-category links, language info that will be nice as the Gemini space grows.
At the moment, the Gemini space is quite small, and directories can be quite complete, so I'd prefer not to maintain something that will have a very large overlap with a superior solution.
I'll leave gemini://directory.randomroad.net up for 3 months, until the end of April. The source repo will stay beyond that, in case it warrants revisiting in future.This has been a short but fun project. Found a lot of interesting things to read over the last couple of months.