Excal
I think gonzdevour was being sarcastic in the "Don't use them, please, have a nice day." mainly because they want to keep it for themselves
based on rest of post it would seem that the plugin was very reliable for gonzdevour
I've never used a 3rd party plugin but if it is made to the standards of today then I wouldn't see an issue in using it
but 3rd party also means that it updates separate to C2 so not always 0-day updates