There's also Bittorrent's SyncApp to consider, though it's still in alpha:<p><a href="http://labs.bittorrent.com/experiments/sync.html" rel="nofollow">http://labs.bittorrent.com/experiments/sync.html</a>
The service looks very similar to our Build-your-own- Dropbox service Tonido Cloud (<a href="http://www.tonido.com/cloud/" rel="nofollow">http://www.tonido.com/cloud/</a>).<p>We have evaluated Java for the client side like AeroFS. But decided against it and went with a native client.