Since you are on GOG, you do not have Steam files. However, some versions of tModLoader may look for them and crash on startup.
If it says "Play," you are likely already on the latest version. To be sure, click the icon (next to play) > Manage installation > Verify/Repair . terraria 1449 gog verified
Unofficial versions often break multiplayer connectivity. Since you are on GOG, you do not have Steam files
: It serves as the baseline for most modern mods before the transition to version 1.4.5 . GOG Version Performance & Reviews Since you are on GOG