VimAck is renamed to Waldo and can be found at github.com/jtaby/Waldo
Waldo (nee VimAck) got a lot more popular than I was expecting it to be, and the name was always temporary. This also makes it easier to come up with an icon, and finally, it's less confusing considering the competition of ack.vim
If you were one of the super awesome people who forked the project before it was renamed, please run this command to update the URL.
(replace upstream with whatever name you gave it)
git remote set-url upstream https://github.com/jtaby/Waldo.git