The original website of XDN is http://digitalnote.org/
 'Espresso", the cheerleader who promotes (but not developes) XDN
created his own site http://xdndigitalnote.com/ which links "DigitalNote Project"
with digitalnote.org

Then there is a relation between XDN and fantomcoin which I don't understand. (Fantomcoin is a fork of Monero)
https://github.com/xdn-project/fantomcoin/compare/2665aba252a72c3b3449742e233ab3ec3728a3af...c5b04fb494176f40808c6db154d647efc8fda2c4#diff-51365377c405c29d9a1e7db96ed2bc46

A freewallet app that supports XDN is available at
https://play.google.com/store/apps/details?id=xdn.org.freewallet.app

Not 100% sure if freewallet is safe to use or not. Do some research.
If you have syncing problems go to http://dasholator.com/XDN/ for help