A colleague pointed out an interesting conversation by Savio Rodrigues and Matt Asay about marketing, sales models and growth in open source companies. Since I work for the referenced company, I'll steer clear of specific responses. But I think Savio is on to something when he talks about the growth hurdles.
Honestly, I don't think start-up OSS sales & marketing challenges are much different than any start-up's challenges. The issues around inside sales vs. outside sales have much more to do with cost-to-serve and deal size... OSS software is generally a fraction of the cost of proprietary alternatives, so your deals are smaller compared to your proprietary competitors. You just don't have the luxury to send out expensive direct sales people and hope to get to profitability quickly.
The subscription model adds to this challenge. When you sell proprietary software, you generally book all of that revenue now. When you sell a subscription (the predominant OSS model, thanks to RH), you recognize the revenue over the course of the subscription. While it's a great business model for cashflow and building predictable future revenue, it means your expense threshold is much lower than a license company - even though you still have to *book* the same amount of business each quarter. The effects are particularly throttling early in the ramp of the business.
So, start-up open source companies necessarily need low-cost, high-impact marketing tactics. And, by golly, providing awesome software to download for free is a great tactic - it drives a lot of web traffic, builds your brand, helps you get your early adopters, and quickly builds a community of advocates that might buy your value-added services in the future. But the free download tactic is less relevant to the challenges of a mid-sized company: converting the early majority (especially big companies), upselling existing customers, expanding your product portfolio, and doing it all profitably (and without early adopter discounts). That's when you begin to think seriously about your channel strategy and business plan, and start to figure out that you aren't all that much different than other software companies - except for the crucial fact that customers inherently want the value you're selling, which is a great place to be.