Open-source e-commerce framework that is a community fork of Spree, created when Spree lacked clear vision/roadmap and was not actively maintained. Uses the same internal modules as Spree, leading to a parallel ecosystem. Rafael Zamaris cites Solidus in his wroclove.rb 2023 talk as an example of what open source can do when users get frustrated: confusion for newcomers choosing between two similar options, internal debates about which is better, and duplicated maintenance effort across two communities.