There are already lots of Trello clones:

Restyaboard: http://restya.com/board (open source, self-hosted)

Phabricator Projects https://www.phacility.com/phabricator/projects/ (open source, self-hosted, or paid hosting)

Kanban: https://kanboard.net/ (open source, self-hosted, or paid hosting)

Wekan: https://wekan.io/ (open source, self-hosted)

And no doubt, lots more not listed here...

I've used http://lavagna.io for a while on my own servers, but recently I've started using and enjoying https://www.favro.com whose free version has less limitations than the free Trello version.

https://zenkit.com for example. Really like it so far (not trying to run from Trello, as I don't use it much anyway)

Thanks so much for the mention, we're glad you like it! For anyone looking for more info about Zenkit & where we're headed, see here: https://news.ycombinator.com/item?id=13022663

Never heard of it, but this actually looks as if it could replace Trello and Airtable, two products I really like, and then some. Thanks for the suggestion.

Wekan.io is a pretty excellent open source alternative to Trello.

Besides being a good one, it also didn't sound like a terrible idea at first. Boards with cards is a suitable simple application for beginners (or people that are just learning a new environment/language).

Then I remembered my difficulty with finding a proper to-do app. Yes, it will have millions of people make a clone, but it will also have thousands publishing crappy versions.

If I remember correctly, the Pro React book has a tutorial for a Trello clone.