q3ded +set sv_dlURL "http://example.org"
The shell removes the quotes but makes the content be a single argument
for progam args. Quake 3 concatenates all the program args and splits
lines at + or newlines. Then Quake 3 parses them using a tokenizer
that skips unquoted C comments beginning with //. This results in
the cvar being set to "http:".
Escape the quotes so they are passed to the program and the tokenizer
knows not to skip C comments.
q3ded +set sv_dlURL \"http://example.org\"