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 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.