The link to the homepage is dead: Homepage: http://www.grahamdennis.me/pocketbib/
and Graham Dennis the developer has not been responding to request about the dropbox connection issues: https://pocketbib.uservoice.com/forums/182833-general/suggestions/20529442-adapt-to-changes-in-dropbox-expected-september-28
Yes, it seems this software is not available anymore.
Thanks for pointing this out: it is not listed anymore in the jabref’s website.