Intridea is a Washington, D.C., company that builds collaborative tools for the enterprise. Its big release this week was Present.ly, a "Twitter that runs inside the firewall" -- something I imagine most people reading this will either love or hate on sight! It's all built on open source -- Ruby on Rails -- but, again, it's not an open source app itself.

It's something I'm nerving myself to expect more and more -- apps built using open source solutions that aren't themselves open. And again, it all comes down to what you're offering and to whom. In the case of Present.ly, it's for enterprises -- in short, folks who are willing to pay right up front for something guaranteed to be functional and with a company name behind it. (The first 60 days are free and after that it's a very reasonable $1/user/month.)

It has indeed considered a core version that would be entirely FOSS, provided enough development partners were willing to come on board. As with many of the other enterprise-software folks I've talked with, its product already has a full gamut of exposed APIs, so it isn't difficult for them to open it up all the way if it comes to that. It opens up one thing that many people can use, but charges for the things a few people are willing to pay for.

That said, Intridea is no stranger to producing open source software. One of its biggest releases in that space is Scalr, a cloud-computing management application for Amazon EC2 that doesn't cost a dime if you just want to snag it and use it on your own, but also is available as a full paid service. When people get serious about using it for their own app (which is presumably a commercial venture of some kind), it does want to be paid for it, as the Intridea folks put it. Open sourcing Scalr also has drawn attention to the whole gamut of products Intridea puts out, so it's proved to be useful in more ways than one.

I come back again and again to the question of what form FOSS use will take, or is indeed taking right now, in all the different places where software is used. One key insight came to me through Romi Mahajan of Ascentium: the use of FOSS (or any software, when you get down to it) is dictated by three constraints: money, time, and people. If you have only one guy and no money, but plenty of time, then FOSS makes sense. If you have lots of people and lots of money, but no time, then something proprietary (or FOSS-based with proprietary wrappings, or support) makes sense.

What I do wonder about, though, is whether the notion of "just open enough" will subsume "free and open" as both a design and marketing philosophy. For people engaged in making Web apps -- i.e., most of the companies I talked with at Web 2.0 -- "open enough" may well be enough for them and their clients. And if we're headed toward a world that runs heavily on Web apps, "open enough" may end up being a corollary of that.