I just installed this plugin and see what you mean. I think that qualifies it as software are a service. It uses an image that’s loaded from the local copy of that plugin directory but generates a URL like so.
https://www.socializer.info/share.asp?docurl=http%3A%2F%2Ftest.server.host.name%2Fthis-is-a-test-post&doctitle=This%20is%20a%20test%20post
The plugin does not really do much besides that (though the settings page is alright).
The Twitter link on that page generates this URL.
https://twitter.com/intent/tweet?original_referer=http%3A%2F%2Fwww.socializer.info%2Fshare.asp%3Fdocurl%3Dhttp%253A%252F%252Ftest.blog.dembowski.net%252Fthis-is-a-test-post%26doctitle%3DThis%2520is%2520a%2520test%2520post&text=This%20is%20a%20test%20post&tw_p=tweetbutton&url=http%3A%2F%2Ftest.server.host.name%2Fthis-is-a-test-post
Which will share your post with the correct URL but have that www.socializer.info
as the ?original_referer
and use this as the tweet text.
This is a test post https://test.server.host.name/this-is-a-test-post
I don’t think this is a scam (software as a service gives me headaches sometimes) but for the life of me I have no idea why anyone would use his plugin. There are so many other plugins that don’t send your users to a third party site like that.
It doesn’t buy the plugin user anything to do that except that this plugin is light weight database wise but all sharing plugins should be that way.