BitDust is described as 'Imagine a decentralized network maintained by other users just like you. Here all your personal files are encrypted and only you hold the key to unlock them. Completely anonymous and secure' and is an app in the Backup & Sync category. There are more than 10 alternatives to BitDust for a variety of platforms, including Windows, Linux, Mac, Online / Web-based and BSD. The best alternative is IPFS, which is both free and Open Source. Other great apps like BitDust are ZeroNet (Free, Open Source), Freenet (Free, Open Source), I2P (Free, Open Source) and GNUnet (Free, Open Source).
IPFS is a global, versioned, peer-to-peer filesystem. It combines good ideas from Git, BitTorrent, Kademlia, SFS, and the web. It is like a single bittorrent swarm, exchanging git objects. IPFS provides an interface as simple as the HTTP web, but with permanence built in.
GNUnet is a framework for secure peer-to-peer networking that does not use any centralized or otherwise trusted services. A first service implemented on top of the networking layer allows anonymous censorship-resistant file-sharing.
Sia is a new decentralized cloud storage platform aimed at giving users control of their data. Data is split into hundreds of erasure coded pieces and encrypted locally, and then each piece is uploaded to a separate host.