As of this writing, 69 questions are tagged
What value does this tag provide (if any), and what guidelines should we provide in its wiki to encourage correct use?
I don't think this tag provides any useful information, and we should remove it.
indie is a meta-tag, and describes more the context of the problem rather than the problem itself, which doesn't offer enough improved search-ability to warrant the consumption of an entire tag slot on a question.
Further, the overwhelming majority of questions asked on this site are from non-professional or hobby developers, such that the
indie tag is actually applicable to all questions. Therefore, like
game-development, it's not a valid tag.