What permissions are needed for omega tools to create subtheme
To work, the user that runs your web server needs to have write permissions to the target folder. Typically, you have a user that owns the files and then the web server runs as the group so permissions of 755 (ex. rwxr-xr-x) would work on most files except files/directory that drupal needs to write to (ex. files directory, or in this case, your themes folder).

What you need to do is either 


change group ownership of the ygf folder above to the same user that runs your web server;
or - you can blow open the permissions to the folder (ex. chmod -R 777 ygf) temporarily and then switch it back after this operation.


Regardless, you're probably going want to remove the write permissions on this folder after omega tools has generated the sub theme. Omega Tools just needs this temporarily and it can be risky to have group-writable folders outside of the files directory.