This tag is about the quarterly creative commons data dumps of all public data in the Stack Exchange network Q&A sites.
Quick answer, a Stack Exchange site currently will not be included in the data dump until there has been enough data to pool and send along with the rest of the package.
[A public data dump] won't be necessary until there is more data to work with there.
Data dumps do not include deleted posts or comments, nor do they contain any voting data.
You can read more about the data dumps at the blog.
Data dumps are now hosted at Internet Archive.