We use StreamServe as our OMS and I want to start a discussion on StackOverflow but there is no adequate tag. Is there a way to create a tag without 1500 points reputation?
There isn't. If the tag is relevant, someone with enough reputation will retag the question to include it. Also, be careful with posting a discussion. If it is not a direct question with regards to a programming problem with the software, it will most likely get closed, and creating the tag would be useless anyway.