This is a well known fiction of the bards of the world. Well... mostly. When a bard tells you the code requires them to act in a certain way, know that it is almost certaintly a lie. A well crafted, lie to be treasured no doubt, but a lie none-the-less. The bards meet in secret when their paths cross to share the new additions to the code they've made. Some of these will even become common enough that all the bards of the world might know that part of the code.
Just as important, if not moreso, as the laws of the code are the exceptions to those laws. A good bard always has a reason why they need not follow the code the way they always have before. This is just another part of the artistry that is being a bard.
What are those rules that almost all bards can agree on? Why the sanctity of fine alcohol, music, and stories! No bard worth their salt will let these things be destroyed if they can reasonably save them, and there is no greater sin than for a bard to go out of their way to destroy so they might have the only song. A true bard knows that a song's power isn't that of a secret, but quite the inverse. Only by spreading, by being known on the lips of every man, woman, child, and creature can it become perfect. And the same also goes for bards themselves... only by sharing their adventures can they grow to be more than mere mortals.