If it didn't happen on the mailing list it didn't happen at all.... with all it's implications this seems to be the hardest lesson for newcomers to the Apache way of development to learn.
In the minimal sense it means that any decision a project takes has to be taken publicly, preferably in some archived, searchable medium. In a wider sense it's usually interpreted as:
- ... don't ask people getting started questions privately by mail, rather go to the user mailing list.
- ... don't coordinate and take decisions in video conferences, rather take the final decision on the dev mailing list.
- ... don't ask people privately on IM, rather go to the user mailing list.
There are even canned answers that can get sent out to those asking privately.
This concept seems to be very hard to grasp for people: As a student, developers tend to be afraid to ask "stupid questions" - it's easy to say that "there are no stupid questions, only stupid answers" - truly feeling this to be true can be hard though in particular for people who are just beginning.
However (assuming the question hasn't been answered before or the answer wasn't easy to find with a search engine of your choice) asking these questions is a valuable contribution: Chances are, there are a couple other people who would have the same question - and are too shy to ask. Chances are even bigger that those developing the project would never think of documenting the answer anywhere simply because they do not see it as a question due to their background and knowledge.
For researchers in particular on their way to getting a PhD. the problem usually is the habit of publishing facts only after they are checked, cleaned and well presentable. When it comes to developing software what this approach boils down to developing a huge amount of code hidden from others. The disadvantages are clear: You get no feedback on whether or not there would be simpler/faster approaches to solving parts of your problem. Developers of the upstream project won't take the needs for this extension into account when rewriting current modules or adding new code. As a result general advise is to share and discuss your ideas before even starting to code.
Even for seasoned software engineers this approach tends to be a problem when not used to it: In a corporate environment feedback on code often is perceived as humiliating. As much as we preach that a developer isn't their code so feedback on coding issues is not to be taken seriously it still takes a lot of getting used to when suddenly people give that feedback - and give it in the open for everyone to see.
Also often decisions are taken privately before communicating publicly in corporations. As a result having heated design discussions tends to feel like a major marketing problem. Instead what is achieved is making the decision process publicly visible to others so they can follow the arguments without repeating them over and over. It also means that others can chime in and help out if they are affected (after all the second mantra is that those who do the work are the ones who ultimately take the decisions).
Again another reason could be for people new to the project or new to some role in the project that asking trivial questions looks intimidating. Again - even if you've contributed to a project for years noone expects you to know anything. If any piece isn't documented in sufficient depth asking the question provides a track record for others to later refer to. It also means you tend to get your answer faster because there are more people who can answer your question. Oh - and if you don't get an answer chances are, everyone else is in the dark as well but was just not asking.
One final word: One fear many people seem to share when asking is to make their own knowledge gaps and flaws public - not only to peers but also to current or future superiors. There's three parts to the advise that I tend to give: Everyone once started small. If your potential future manager or team mates don't understand this, than learning and making mistakes obviously aren't welcome in the environment that you are aspiring to join - is it really worth joining such an environment? Even so you start small, if you continue to contribute on a regular basis the amount of information that you produce online will grow. Guess how much time people spend on evaluating CVs - it's very unlikely they will read and follow each discussion that you contributed to. And as a third point - do assume that by default everything you do online will be visible and searchable forever. However chances are that ten or fifteen years from now what you are writing today will no longer be accessible: Services go away, projects and their infrastructure die, discussion media change - anyone still remember using NNTP on a regular basis?
As an exercise to the reader: Before writing this post I spend a couple of hours trying to dig up the mails I had sent I believe in 2000 to the I think KURT and RTLinux discussion lists in order to prepare some presentation about the state of realtime Linux back at university. I search the web, search the archives I could find, searched my own backups from back then - but couldn't find anything. If you do find some trace of that, I owe you a beer next time we meet at FOSDEM ;)