Making your own version of Helm's Deep is a right of passage for new map designers. There are few moddable games out there that do not have their own version of Tolkien's castle. (I was pretty taken by the one in Far Cry 3). However, Helm's Deep Reborn is different from most versions of the map; Helm's Deep Reborn has been officially endorsed by Valve and is currently being hosted on their official Left 4 Dead 2 servers.
More on Valve's love of the orcs below.
It's all been in aid of showing off a recent server update Valve have implemented. Writing in a blog post, they say they "fixed an issue with dedicated servers and workshop content. This should resolve some of the consistency issues people are seeing while playing on a dedicated server. [...] Server operators will need to move workshop content from addons to addons/workshop for it to work correctly".
It's a small fix but eases the gripe of having to redownload a mod whenever it receives and update.
If you want to get on Valve's servers official servers, and all the stable play that they offer, then you'll need to subscribe to the collection here and then "Make sure to choose official servers when you play to join one of our servers. It is a survival only campaign, so it is not playable in other modes". So set the filters up and it should pop up in the search results.
I'm looking forward to giving this a try. I sunk many, many hours into Left 4 Dead but had run through my addiction to the game by the time the sequel came out. I think I'm about ready to jump in and see what 2 has to offer.
See the mods created by Tsar, SeriouS_Samurai, The Fish, and Splinks at work in this video: