Currently, OAuth applies change tags to edits made by an OAuth consumers. However, it does not implement the `ListDefinedTags` hook to actually define those tags.
Currently, all this does is to make the OAuth tags show up as "inactive" at Special:Tags, even when the OAuth consumer is still active. However, with the work being done on T20670, this may become more of a problem.
You can see this in action at [[https://commons.wikimedia.org/wiki/Special:Tags|commons:Special:Tags]]: the "OAuth Uploader" tool shows up as "inactive" even though it is clearly not.
OAuth should become a responsible user of change tagging, and define tags relating to active consumers. When a consumer becomes inactive (up to you how you decide this) the relevant tag should not be marked as "active" any longer, to avoid a misleading display at Special:Tags.