I was thinking of writing a post for the blog, and found the FAQ. It links to a blog chat room which is dead, and it is entirely unclear whom to contact about writing posts.
Is it actually dead? There hasn't been activity on it for 7 months. But it's not so dead yet that we've removed it.
So the short answer is no, it's not technically dead. (Although it's unclear if it has a pulse).
The liveliness of the blog feeds on itself, I think. An active blog has more presence and solicits more contributors than an inactive blog. If you have something you would like to contribute, I recommend going for it. If you have a blog, it's also fine to post both on your private blog and on the Math Community Blog.
If you would like to contribute a post, you can use the chatroom (which I've unfrozen). Alternately, I've handled most (but not all) additions to the blog, and you can just get in contact with me.
To contribute, you must first log into the blog once (this needs to be done only once). Then you need to ask one of the site moderators to give you draft access (usually through the chat room). Then you write a post, and notify the site moderators (also usually through the chat room) that you're done. Every thing that gets here gets read by a few people before being officially posted.
In the past, there were a few community members who stepped forward to be maintainers of the blog. But I'm hazarding a guess to say that after so many months of inactivity, sticking with the site mods would be your best bet for now.