When running a free software project, you won't need to talk about such weighty philosophical matters on a daily basis. Programmers will not insist that everyone else in the project agree with their views on all things (those who do insist on this quickly find themselves unable to work in any project). But you do need to be aware that the question of "free" versus "open source" exists, partly to avoid saying things that might be inimical to some of the participants, and partly because understanding developers' motivations is key to managing a project well.
Free software is a culture by choice. To operate successfully in it, you have to understand why people choose to be in it in the first place. Coercive techniques don't work. If people are unhappy in one project, they will just wander off to another one. Free software is remarkable even among intentional communities for its lightness of investment. Many of the people involved have never actually met the other participants face-to-face. The normal conduits by which humans bond with each other and form lasting groups are narrowed down to a tiny channel: the written word, carried over electronic wires. Because of this, it can take a long time for a cohesive and dedicated group to form. Conversely, it's quite easy for a project to lose a potential participant in the first five minutes of acquaintanceship. If a project doesn't make a good first impression, a newcomer may wait a long time before giving it a second chance.
This potential transience of relationships is perhaps the single most daunting task facing a new project. What will persuade all these people to stick together long enough to produce something useful? The answer to that question is complex enough to occupy the rest of this book, but if it had to be expressed in one sentence, it would be this:
People should feel that their connection to a project, and influence over it, is directly proportional to their contributions.
No class of developers, or potential developers, should ever feel discounted or discriminated against for non-technical reasons. Clearly, projects with corporate sponsorship and/or salaried developers need to be especially careful in this regard, as Chapter 5, Organizations and Money: Businesses, Non-Profits, and Governments discusses in detail. Of course, this doesn't mean that if there's no corporate sponsorship then you have nothing to worry about. Money is merely one of many factors that can affect the success of a project. There are also questions of what programming languages to choose, what license, what development process, precisely what kind of infrastructure to set up, how to publicize the project's inception effectively, and much more. Starting a project out on the right foot is the topic of the next chapter.
 There can be cases where you discriminate against certain developers due to behavior which, though not related to their technical contributions, has the potential to harm the project. That's reasonable: their behavior is relevant because in the long run it will have a negative effect on the project. The varieties of human culture being what they are, I can give no single, succinct rule to cover all such cases, except to say that you should try to be welcoming to all potential contributors and, if you must discriminate, do so only on the basis of actual behavior in the project, not on the basis of a contributor's group affiliation or group identity.