Professional Open Source Software (POSS) companies exist as an exchange system between two sets of consumers: an open source community (motivated by mutual contribution) and a mainstream market (motivated by economic rewards). Organizations in need of support, services, training etc contribute financially for those services as paying customers. That money is used by the POSS company to pay for full-time resources (engineers, product managers etc.) whose efforts (the majority, if not all of it) end up as open source software, freely available to an open source community. The open source community contributes to the software by helping improve the design, functionality, quality, translations, and documentation of the software. The improved software attracts more customers and the cycle continues, hopefully perpetually. In this model all three parties gain:

My analogy to this is 'The Bee Keeper'.

The Bee Keeper creates an environment that is attractive for bees: accommodation and a natural, food-rich habitat. The bees do what they do naturally and make honeycombs. The Bee Keeper sells the honey and bees-wax to his customers and uses the money to grow his bee farm.
The analogy goes a little deeper.

Customers are corporations, the community are people. They have very different needs that need to be met.

This inherent distinction between customers and community is important when it comes to attempting to turn members of the community into customers. The sales and marketing groups within a POSS company need to be aware that, in most cases, it is not possible to convert a community member into a customer. However is it possible to convert the employer of a community member into a customer. Slamming community members with a marketing pitch is unlikely to achieve this.

Community members have the potential to persuade their employer to become a customer. The members themselves typically have no budget or no control over how the budget is spent. A POSS company needs to educate its members on the services that are available and the long term advantages to everyone if those services are used. The POSS company needs to find a way of presenting this and enabling members to present it to their employer without de-valuing the capabilities of the community member.

Next - The General Model