From The Open Road...

In an open-source business, a vendor's biggest competition often
derives from a freely available, "community" version of its product. By
extension, an open-source vendor's biggest competition comes from the
systems integrators that provide implementation services around that
vendor's community software.

Crippling this competition--so tempting on the surface--tends to
cripple all the benefits that come from it, including facilitated
adoption of the software, and lower sales and marketing costs.

The question, then, is how to foster unfettered adoption of one's
open-source software while still preventing would-be partners from
undermining one's own ability to profit from the software.

The post goes on to describe 5 strategies Alfresco uses...

http://www.cnet.com/8301-13505_1-9934560-16.html