BigchainDB is described as 'With high throughput, sub-second latency and powerful functionality to automate business processes, BigchainDB looks, acts and feels like a database with added blockchain characteristics' and is an app in the Bitcoin & Cryptocurrency category. There are three alternatives to BigchainDB for Linux, Mac, Windows, BSD and Android. The best alternative is CouchDB, which is both free and Open Source. Other great apps like BigchainDB are RethinkDB (Free, Open Source) and CouchBase (Free, Open Source).
Apache CouchDB is a distributed, fault-tolerant and schema-free document-oriented database accessible via a RESTful HTTP / JSON API. It includes incremental map / reduce mechanics for queries and keeps data safe with an append-only datastore.
RethinkDB pushes JSON to your apps in realtime. When your app polls for data, it becomes slow, unscalable, and cumbersome to maintain. RethinkDB is the open-source, scalable database that makes building realtime apps dramatically easier.
Couchbase is the NoSQL database market share leader, with production deployments at AOL, Deutsche Post, NTT Docomo, Salesforce.com, Turner Broadcasting Systems, Zynga and hundreds of other organizations worldwide.