So, I installed invite on a non-MU site. Upon installation, without even activating, a page appeared saying that it was only to be used with MU sites. Every page I loaded on the site, front or back end would give that error.
Going into FTP to uninstall the plugin was the only option for moving forward.
It would be great if this error message was less intrusive and less of a hassle to remove. Thought you ought to know.
Thanks again for all your hard work!