There is a tag zbar-sdk on SO, but [tag:zbar sdk] is something that regards only to iPhone backend of zbar. I see some questions, maybe 10%, regard to zbar in general or to other ports, like Windows or Linux. I suggest adding also a zbar (or zbar-other) tag and explain that it's about non iPhone questions. In the same time an explanation should be added to zbar-sdk tag, that it's only for iPhone questions.
I think having 2 separate tags for zbar is the best option. I could get only non iPhone questions with zbar query. But if you prefer to have only one, then it should rather be "zbar".
This is not very important, but since I started trying to change this (by flagging this question as an example) and was adviced to post a retag-request - I do.