A bit of major announcement in regards to Lightning (Calendar) and the upcoming Thunderbird 3. From David Ascher’s (CEO, Mozilla Messaging) Blog:

For some time, we (the Thunderbird release-drivers) have been exploring how to best integrate calendar functionality into Thunderbird.  Time for an update.

The current plan is to work with the Lightning Add-on community to make a version of it available as an add-on to Thunderbird 3 after we ship later this year.  This is a change from our initial plan of integrating all of Lightning into Thunderbird by default.

While there are several reasons for this decision, these two standout the most:

1. we try to avoid feature changes in between major releases, and limit minor updates to security fixes.  This would mean that feature changes to Lightning would have to wait for the next major release of Thunderbird.
2. …we recognize that different users need different kinds of calendaring solutions.  Just as there are more and more messaging systems, there is a growing diversity in calendar usage models, such as web calendars, stand alone clients, and calendar and event applications on social networking platforms

To put #1 in perspective, consider if AdBlock Plus and NoScript (two of the most popular and frequently updated Firefox add-ons) were standard parts of Firefox. If this were the case, any feature changes to these add-ons would have to wait to be implemented into the next major release of Firefox. In regards to #2 I know some individuals who did not want to see Lightning to be an integrated part of Thunderbird 3, complaining it would make TBird too much like Microsoft Outlook.