What one says after realising one has said a slightly racist, sexist, homophobic or other comment in front of a person of the supposedly offended social group. The person will typically reply with "None taken"
When not living up to the more or less formalized agreements for collaboration within a collaborating group, thereby causing some small amount of pain for all collaborators. The implied penance is buying or baking cake or similar goodies for the entire group.
In software: a cakeable offence could be committing a breaking change, causing tests not to pass, or projects not to compile