I just tested it and it works!
You can normally find these download url’s by logging in to these premium plugin accounts and look for the download page. There you normally have download links to the latest version of the plugin.
So adding this to your composer.json lets you install two very popular premium plugins using composer:
"repositories": [
{
"type": "composer",
"url": "http://wpackagist.org"
},
{
"type": "package",
"package": {
"name": "advanced-custom-fields/advanced-custom-fields-pro",
"version": "5.3.2.2",
"type": "wordpress-plugin",
"dist": {
"type": "zip",
"url": "http://connect.advancedcustomfields.com/index.php?p=pro&a=download&k=LICENSEKEY"
}
}
},
{
"type": "package",
"package": {
"name": "gravityforms/gravityforms",
"version": "1.9.14.25",
"type": "wordpress-plugin",
"dist": {
"type": "zip",
"url": "http://s3.amazonaws.com/gravityforms/releases/gravityforms_1.9.14.25.zip?AWSAccessKeyId=ACCESSKEY&Expires=EXPIREDATE&Signature=SIGNATURE"
}
}
}
],
"require": {
"php": ">=5.5",
"composer/installers": "~1.0.12",
"vlucas/phpdotenv": "^2.1",
"johnpbloch/wordpress": "4.3.1",
"roots/soil": "^3.6",
"advanced-custom-fields/advanced-custom-fields-pro": "5.3.2.2",
"gravityforms/gravityforms": "1.9.14.25"
},
After adding this, just run composer update
!