Our friend Francois Rey is a big fan of the Collaber collaborative software. See http://blog.collaber.com/

He recently sent them a blog posting which outlines not just the benefits of going ‘open source’, but gives an indication of different hybrid business an licensing models which may have the effect of creating a convergene between business and community interests.

Francois Rey at http://blog.collaber.com/archives/7#comment-621:

I believe making the product open source would be your smartest move: it would give you a key differentiator with MS Groove and would allow your network to grow faster than what the proprietary approach could do. With a growing network, the opportunities for a company to provide additional products and services grows accordingly.
Groove is already well established and mature, and is likely to grow in the corporate world since it’s bundled and integrated with Office Enterprise. Adopting a strategy where you are head-to-head with MS is asking for trouble and would require serious motivations. Groove 2007 is included ‘for free’ in Office Enterprise edition, and a price war with MS is not desirable.

Instead, try to develop your business where they can’t: go open source and integrate with other open source initiatives such as Jabber, which is a well established network, and also a good example of a both non-profit (Jabber foundation) and commercial company (Jabber Inc.). While the foundation manages the development of the open source technology, the corporation deploys it in the corporate world through its service offering. You might want to get in touch with them to get some advice.

If you like to ensure you have a sufficient return on investment, you could go open source progressively.
For example you can make the client free and open source, and keep the relay server proprietary for a certain time. In doing so make sure the community understand your commitment to open source and your need to recuperate your investment.

Another approach since you own the source code is to have dual licensing like VirtualBox is doing, and keep the features targeted to business use proprietary, see http://www.virtualbox.org/wiki/Editions.
Make the public server free, but ask for a fee when its comes to setup a private server.

You already use Eclipse RCP, so making the move to open source should not be such a major undertaking provided that you followed the modularity and coding standards.

Being based on RCP also means that you can possibly make Collaber easily integrate into Eclipse IDE. If not already done, you perhaps could also benefit from Eclipse Communication Framework, and vice-versa.

Which gives me another great idea: integrate with an open source SCM like SVN or GIT, or better, make your own distributed SCM within Collaber, making it easy for people to collaborate without the need to have a server.

Believe me: the open source community is much more “receptive” to your product than the business community, simply because it understands the need to collaborate and go beyond the corporate boundaries. If you embrace already existing networks and communities such as the one around Jabber and Eclipse, you have a wild fire propagation and an opportunity to develop a collaborative network much faster than what MS can do.

See also the other similar thread at http://miragroupware.org/forums/index.php?topic=30.msg230#msg230