Posted September 17, 2019
As Marko said, a lot of the steamapi.dll files in GOG releases are indicators of a "common release" thing, ie, the dev will bundle all platform's .dll's with all releases and just link to the relevant client in question. Eg, deleting both steam_api64.dll files you mentioned for the GOG version of Oxenfree (as well as CSteamworks.dll in the plugins folder), makes zero difference at all to the game starting up, so they're probably just "inert" files that aren't linked to at all. Sometimes you'll also see the reverse of Galaxy64.dll / GalaxyCSharp.dll files bundled in Steam releases.
UhuruNUru: I was using it to point out that running without the store client, and being DRM free are two different things, not that it should be on a list. Again my point was requiring the API/SDK does NOT make it DRM, and is most likely got something to do with the achievements, or lazy devs doing minimum work to get it working on GOG.
I don't know if the ability to use -EpicPortal switch to run without the Epic client is a feature or a bug, but it's been there unpatched for quite a while now so I'd assume it's intentional?
UhuruNUru: My point was it doesn't appear as though it's meant to be DRM free, but Epic levels of incompetence, make it that way.
I know what you're saying and I prefer the "pure" offline client-less versions especially of older games too. Eg, despite being DRM-Free, I did notice that the GOG version of Bioshock Classic takes almost 12 seconds to start whilst the Humble DRM-Free offline installer version (that doesn't call any client) starts instantly. I'm guessing that's something to do with Galaxy integration for achievements, cloud saves, etc. In fact, GOG Bioshock (inc Classic) is listed W7 min whilst Humble's supports Win XP, so that could be the same reason (Galaxy is W7 min too).
UhuruNUru: I like DRM free, but no Store Client is more important to me. If I could choose between using EA's Origin (Currently DRM, and Store Client), with No DRM, but still have to use the Store Client, or having an offline form of DRM, and no Store Client, I'd take the No Store client every time.