Restyaboard is rather similar to Trello and other Kanban based services. Unlike most of them however Restyaboard is open source and it comes with a lot of functionality. If you like the simplicity of Trello, but you need a bit more functionality or you just don't want that additional cost, then Resyaboard could be a viable alternative.
Restyaboard is easy to work with and the features are pretty impressive. They have put together an extensive list of features that is then matched with Trello for comparison. You can check that out here.
Restyaboard is open source so you can download it from GitHub. You can also get it installed in the Cloud by using Digital Cloud's droplet feature. Some of the plugins comes with an additional cost so that is something to keep in mind however.
Overall this is not a bad Trello alternative. There are other alternatives out there, but Restyaboard sticks out a bit because it is open source and since you can have local installations rather than cloud based.