Appa (named for the sky bison in Avatar: the Last Airbender), is a joint effort by Fission (mainly Philipp Krüger, number zero (mainly dignifiedquire), and others to make incrementally verifiable & incrementally synchronizable encrypted at rest data available over IPFS. It’s essentially a mashup of Iroh, the Webnative File System, and FUSE.
External Links
Mascot
An image that I generated via Midjourney for the project: