Connect to Screen Sharing (VNC) using Debian/Ubuntu?
Yes, it is possible to connect to an OS X host using VNC.

It seems, however, that your method of turning it on from the command line doesn't work.

Instead, try 

sudo defaults write \
/var/db/launchd.db/com.apple.launchd/overrides.plist \
com.apple.screensharing -dict Disabled -bool false
sudo launchctl load -w /System/Library/LaunchDaemons/com.apple.screensharing.plist


To test it I'd install telnet one the host Mac (you can do it with homebrew - brew install telnet and then try telnet localist 5900 which should get a connection. Then try the same from your Debian box. Once you know you can get a connection from the Debian box try your VNC client.