Use Google Tasks in Thunderbird?

Use Google Tasks Sync for Mozilla Thunderbird. It requires Lightning for calendar support.

One interesting workaround for this problem, whilst we're stuck waiting for tasks API, is to use Bryan Clark's Google Calendar Tab. As long as you have your tasks displayed on your Google calendar, you will then have access to them from Thunderbird too.

Obviously this isn't as good as native integration into Thunderbird via an API, but its the best I've managed so far.

Google has released the Google Tasks API in May 2011. There's a getting started guide on the Google apps developers blog. The GDATA Provider developers track the issue but it hasn't been resolved yet.

There is no way to directly sync, one problem being that 'Google Tasks' are far simpler than 'Thunderbird Tasks'. Howerver, "Google Tasks Sync 0.3.1" is a currently working addon that pops up in the Task daily pane to the right of the calendar and email (when daily pane view is active) and presents the Google Task system nested neatly there. It's not a web browser view of Google's own 'Tasks' window, but a proper, native add-on, consistent with Google's task system and synced with it. It means that the very good T'bird task management is bypassed, and there is an initial signing in process the first time that you use it, but other that that, it works very well.

It is definitely possible without a published API because I use a product called gSyncIT to sync tasks from outlook to google tasks. Unfortunately their product is only for Outlook and not Thunderbird/Lightning.