Rated 5 out of 5 stars

This is a terrific Add-on, especially considering that SunBird Calendar is no longer under any real development. Using the "lightening" extension plugin in Seamonkey, Lightbird adds an additional separate calendar component, that can be used as a stand alone Calendar . Running the Lightbird Calendar in Seamonkey by itself runs at about 110-140 M ram.

My experience using the Lightning extension on Seamonkey which is required to make Lightbird work:
You must find and download the Lightning extension from its "Beta" page, to make it work on Seamonkey.
If you use a local calendar, note where the ".ics" file is for each calendar OR
export your calendar as an ICS file to your own customize folder location and reopen (File -> Open calendar)... this because Lightening tends to break on new Seamonkey updates... however the local ics files are still preserved if you need them immediately. together lightning, lightbird and Seamonkey are a good calendar option.

This review is for a previous version of the add-on (0.3.1). 

Rated 4 out of 5 stars

It gets five stars if I can figure out how to launch it as a console command... i.e. seamonkey -addressbook for seamonkey address book. Then it could be binded as its own component like the other seamonkey/ice-ape components .

This review is for a previous version of the add-on (0.3.1). 

You can use
seamonkey --chrome chrome://lightbird/content/sunbird/calendar.xul
for now. :)
The proper option will be -calendar, but it doesn't work yet.

Edit: Fixed for the next version.