The community is helping lay the code.
its an open source project, meaning the code for each release is publicly available as its developed (no one could really trust it otherwise). There are many devs who work on and update the code. Final release say is by gavin andreesen. See bitcoin.org for more info.
I find that highly centralized (in a different way than how this word is used typically when talking about bitcoins) when one person has a "final say" on the code itself. I was reading threads about how major changes wouldn't happen like deleting extremely stale coins and such (again I know it won't happen), and it got me thinking about who could make this happen if it was to happen.
What is centralized is the average person's mentality to get their client from bitcoin.org.
You could copy the source code and make your own modifications. If you could convince people to use the client you built, then Gavin wouldn't have any say in the matter. As best as I can tell "The Bitcoin Foundation" (and as such Gavin) have control of the bitcoin.org domain and as such have the "final say" in what is posted there as their "official release". You are welcome to create your own website to distribute your modified code.
