You are reading a single comment by @Fox and its replies.
Click here to read the full conversation.
-
It doesn't look like it's the Steam version.
Shouldn't matter, you can still launch it from within Steam
https://support.steampowered.com/kb_article.php?ref=2219-YDJV-5557
You can add any games to steam by their product key. Usually if you buy from CDKeys or the like they just give you the key, then from within Steam you use the Add Game, input the key and download.
The main downside of buying from a place like CDKeys is there's a chance the key was stolen or cracked, so may be revoked without notice in the future, however the bigger websites like CDkeys and All Key Shop are generally very good at replacing any keys which get revoked.