The Steam version (Quake 3 Arena is not sold standalone on Steam anymore, but is included in Quake Collection ) originally required Steam to be open, not a CD. However, to bypass the Steam client, you can use the +set com_ignorecrash 1 trick, though ioquake3 is still superior.
Are you tired of needing the CD to play Quake 3 Arena? Look no further! A no-CD patch can allow you to play the game without the disc, and we've got the information you need. quake 3 arena no cd patch link
This is a smaller executable update that replaces the older game engine and addresses security exploits. The Steam version (Quake 3 Arena is not
: The most widely used source port. It is open-source and requires you to simply copy the pak0.pk3 file from your original disc to the baseq3 folder. Download it at ioquake3.org . Look no further