Chedo: You think this is a Steam version and for some reason I deleted the .dll file? No, it's the latest GOG 3.0.1 beta. The solution works though.
Past GoG OW's had the steam_api.dll included. I do not control what Bohemia puts on GoG, so if they have missed out the steam_api.dll then the game isn't going to run while also having OWSteam.dll . Bohemia never actually asked me which files are needed on GoG.
3.0.1 beta also isn't an Original War version. I don't know why Bohemia is using some random version numbers on GOG as that is not what the game version is. Original War should be on 3.0.8.246 just like steam.
The latest version is currently 3.0.9.282 (Which can be found on the OW Discord)
P.S There is no such thing as a "Steam Version" or a "GoG Version". OW does have support for Steam's API but that does not mean its a Steam Version. You can use the patches/etc on any "version". GoG and Steam should have the exact same files (Unless Bohemia misses some out). Technically steam_api.dll should be included on GoG as OW patches contain OWSteam.dll though i can account for it in future versions.