Future versions of OpenOffice.org will come bundled with Mozilla's Thunderbird email client and Lightning calendar application.

The open source office suite is also planning to revamp its system for building and installing extensions by the end of the month by introducing an extensions system like that of Mozilla's Firefox browser. The process of developing, selecing and managing extensions will be standardised and simplified, according to Charles H. Schulz, the lead of OpenOffice.org's Native Language Confederation.

Developers disclosed the new developments at last week's OpenOffice.org Conference in Lyon, France.

Extensions of various kinds are critical to enterprise users of productivity software, who often add elaborate customised services to the software's basic functions. Companies' heavy investment in macros for Microsoft Office is considered one of the major barriers to adoption of OpenOffice, despite the existence of tools for migrating such macros.

OpenOffice will get "Firefox-like" extension capabilities by version 2.0.4, due this month, Schulz said. The suite's existing extensions platform will get a new and "definitive" extensions format, .oxt, which can work with languages from StarBasic to Java.

The suite will get new extensions wizards and configuration tools for the benefit of end users, Schulz added.

Reaction from developers on the Internet was mixed, with some pointing out that a more open extensions framework could be a potent new attack vector. Mozilla has had to tweak Firefox's extensions system in the past to deal with security concerns.

Both OpenOffice and StarOffice will be available in Thunderbird and Lightning bundles, Schulz said, but there's no timeline set for releasing the bundles. "Connectors to Sun Calendar Server and Microsoft Exchange will also be developed," he said.

Some developers joked that OpenOffice is already bloated enough without being included in a bundle with two more applications. "It's just the natural order of things, as expressed by Zawinski's Law of Software Development: 'Every program attempts to expand until it can read mail'," wrote one developer in a Slashdot forum.

Schulz said plans for version 3.0 are still up in the air, partly because of a change to the release process earlier this year, which made releases more regular and incremental. "The only objective of the 3.0 will be to make it much more modular and running on top of frameworks such as Eclipse, Netbeans and Mozilla's XUL," he said.