Transparency should be applied to how decisions can get made in FOSS communities. This can involve different layers; for example, transparency could apply to:
1. Who gets to participate in decision making.
2. How these people are selected.
3. The process of decision making.
In FOSS communities I think transparency should apply to all three where reasonably possible. What do I mean by this? Let's take a couple of examples:
A) Getting hired by a FOSS organization which is integral to the community.
B) Getting commit access to an svn repository.
C) Getting syndication of one's blog onto a planet/aggregator.
A FOSS community might decide on the following transparency for each example:
For A: Transparency of 2 only.
For B: Transparency of 1, 2 and optionally a moderated version of 3.
For C: Transparency of 1, 2, and 3.
How might the transparency by realized?
Let's take example C, the blog syndication; the decision maker(s) should be known, perhaps listed right on the planet. The way the decision makers were chosen should be known, this could exist on a wiki page, perhaps in the governance section of the project wiki site. The decision process could be made transparent by requiring a public trac ticket for every blog that gets added, with the required number of decision makers commenting on the ticket directly, for all to see. As an added bonus, the community could chime in on the ticket with opinions.
Transparency can help avoid conspiracy theories.