That is possible. I wonder if thread would have been created had you just made topic Wolfenstein.
I almost changed it to CSGO/Wolfenstein last night but around here it might have attracted some strange answers. Not helpful ones.
I don't actually have an answer to main question. I just like mysteries.
Here is a link to the developer of the game (splash damage) website. There you can download the full game, as for the MP, you might need to do something special, i would ask this question on their forums that they have a link to on the page as well.
As for the CSGO problem, i dont know what to tell you. They had it seperated between Competitive and non-competitive modes. If youre looking for a match with real people, youd go under competitive, im not sure what the set up is like now though because i havent played it in a while.
Last time I played ET there were still servers active and some of the old community members were still around. That was a few years ago though, but I still think about jumping back in. Was a great MP game.