Sample for save and download
To run the sample just download or clone this. For setup follow the same procedure as documented here http://developer.yahoo.com/mail/docs/user_guide/GettingStarted.html
php SaveAndDownload.php JSON < consumer key > < consumer secret >
For SendMessage
php SendMessageOauth.php < consumer key > < consumer secret > < from-emailid > < to-emailid >
License is same as https://github.com/ramiyer/YahooMailApiSample/blob/master/LICENSE