This Plugin is working only with wp-config.php file.
There is not Database Table created or any Database interaction.
It acts only with two Database functions: update_option() and get_option(). Those’re WordPress functions. Nothing else..
The Plugin is risk and this mentioned in the Plugin page.
You should know what are you doing. You also should be aware that any custom fields will be erased. I also mentioned this in the Plugin Page notes.
MU will be down with no doubts as the Plugin is not supporting MU Config Options. It wont write MU constants. However once the config file is fixed everything would work fine but never corrupt Database. I’m SURE
You need to read author Notes and Waning before using Plugins.
Thanks,
AHMeD