I wonder why they didn't use something like CouchDB for this purpose and instead engineered their own solution? I see the CouchDB replication protocol + conflict detection perfect for their usecase.
I often wonder why CouchDB didn't take off more. It wasn't a panacea but it was clever enough and you could use it in mobile apps. Perhaps the decision of the "host" company to merge with another company and head in the direction of CouchBase made people wary. Or there's some technical reason I'm not aware of. The latter seems more likely.
I am one of the original CouchDB folks, and a cofounder of Couchbase. We have spent the last few years quietly building an enterprise-class suite of Couch sync compatible databases. Everything we do is open source and Apache licensed.
[edit] we've been able to do this, funded by the success of Couchbase Server. Which looks like a high-performance NoSQL database, not an offline mobile database, but it uses many of the same data structures.
Yes, although we have a release of 2.0 coming up, and the PouchDB project is really active. The problems couch can solve (e.g data safety and offline capability) probably aren't considered when initially building a product. Also moving from SQL to CouchDB is quite tedious, although my company just went through that process :)
There are also other models, sharding individual databases per user or some other application logic. There are definitely some use cases we dont handle amazingly right now, but its all heavily being worked on.