Because WildStar is abandonware (no longer sold or supported by NCSoft/Carbine), distribution exists in a legal grey area. The developers of emulators cannot host the client files themselves, as the IP belongs to NCSoft. However, they point to community archives.
"WildStar 16042 client" likely refers to a specific build/version identifier for the WildStar game client. WildStar was a sci‑fi MMORPG developed by Carbine Studios and published by NCSoft, launched in 2014 and officially shut down in late 2018. Community interest since shutdown has centered on archived builds, private servers, modding, or preservation projects; a string like "16042" typically denotes an internal build number, patch revision, or executable/installer version used by players, server operators, or archivists to reference an exact client state.
GitHub - NexusForever/NexusForever: An emulator for the defunct MMORPG WildStar which supports build 16042 (Final Patch) · GitHub.