Help, please. Do I need to download a steam client to play BFGA2?

[Red Pins]

Basically that.

I've ragequit MWO for the last time, I hope.  I'm trying to find a (legal) download for Battlefleet Gothic Armada 2 for PC, but can't find anything - am I overthinking this?  I know a lot of games go through Steam to prevent piracy, is this one of them?

So, will I have to download a Steam client to download the game, kept on the Steam servers?  Or do I get the whole game downloaded onto my computer to keep?  (I really don't want to do this, I'm old enough to want disks or permanent copies of the game of my own.)

Will the developer eventually shut it down and leave me unable to play it?  Or is it just permanently hosted on the Steam servers?  Will I ever lose the ability to play it?

A little miffed I accidently purchased an Xbox live copy from MS - hate, hate, hate their store and how I missed the 'Xbox Live' quote above the title - but I can live with Steam if it means I can enjoy gaming again without getting frustrated.

[Dies Irae]

You can buy BFG:A2 from GOG.com if you set up an account there (it's another electronic sales client similar to Steam. Same but different.)
Their range isn't quite the same as Steam's but if you're looking for an archival friendly seller, it might suit your purpose better.

You can get by without the GOG Galaxy client and they still offer a downloadable installer for archival purposes.

After you purchase it, go to your GOG account library.
From there, you can use the entries in the 'Download Offline Backup Game Installer' to download a copy which will allow you to continue to install the game even if GOG's servers go boom.