This plugin somehow was installed on my site without my knowledge. As the other users explain, it can not be un-installed.
Anyone who is also getting hacked, beware. Parts of my site become un-available to certain users. I was able to remove it by deleting files from the server but I still have not been able to determine how it was installed. We did not have any new users registering.
I suspect that other plug-ins I had installed were corrupted. A few suspects are: user registration, gravityforms and wp-optimize. I’ve seen mentions of simplelender hacks mentioned on gravityforms and wp-optimize pages.
If you have been dealing with this hack, please share so we can identify the source.