Okay, I happen to be a Mac user who also owns this game on steam and DRM-Free, (it's the same version except I believe steam has it in folders while otherwise it's self-contained in the app itself). I don't know about linux but would assume because of the "unix"-or-whatever similarities that it's the same issue.
ALSO: We don't actually know what system he's on so disregard this if you aren't using OSX (Macinstosh)
First off, to get it out of the way:
The OSX (Macintosh) version of CS+ (both Steam and DRM-Free) are completely broken. It hasn't worked since OS version 10.9 (AKA "Mavericks"). That was released in 2013, and NiCALiS-whatever-is-up-with-the-capital-letters has ignored protests to change one line of code to fix it.
Okay, now that my rant is over, I can give the good news. It's a simple fix (IF you have administrative access). Basically what happened is that Mavericks changed syntax for filepath shortcuts or something, so when the launcher attempts to locate the "Data" folder that basically holds the game, instead of being locally directed to the steam folder (or inside itself if it's non-steam), it's instead pointed to the top-directory of the hard drive ( I think windows users call it the C:// root directory drive whatever).
So if you're on OSX, you need to find the "Data" folder and move it straight to "Macintosh HD". That's the simplest way to get it running outside using community patches. If you need further instructions ask me and I'll find more specific instructions I posted here years back.
I should probably just record a video at this point.
