Oops, cl_downloadfilter should be set to all, not none. Have him try that?
Edit: I've just confirmed that cl_downloadfilter to none causes this issue, going to make a news post about it.
Default setting for cl_downloadfilter was "all" (we had both looked at our clients and determined this to be the case), but since process is about changing things and you had asked about this one specifically, he also tried "none" and had the same result.
*edit by author*
He does not have ULib or ULX installed locally. Originally he did receive the Lua Cache file, but has not recently (he's going to flush cache and check that again). Alright, he got the Lua Cache again, but has the same results as before.
On other servers (where the Lua cache is downloaded as well), the print( ULib ) also shows nil, and he is of course unable to see any dialogs including MOTD. He is able to run command-line forms (e.g. "ulx god" works, but throws
"Warning: Unhandled usermessage 'tsayc' "), just no GUI.