Lust from Beyond: M edition - GOG always adds a special edition subtitle to confuse consumers into thinking this version has more bonus stuff in it but it's actually the same game as the one on Steam. It's a trick GOG employs to compete with Steam and get more sales of the game omegalul. It's annoying that they do this because every once in a while you will get a thread on Steam asking if there are any differences between the two. Sometimes there may be differences but most of the time it's the same game.

P.S. Ok, it turns out, the developer released this same game (M edition) on Steam so my assumption of this release is wrong but the point still stands. GOG always adds a special edition subtitle to differentiate games that were released on Steam when it's the same game a lot of the times.

You are wrong. GOG isn't generally allowed to alter the titles of the games, it's the publisher that does that. GOG would be in a huge heap of trouble if they did without the publisher saying it's alright.

Nice non-apology, there. Show me one game that gog changed the name of. Just one. In fact, I doubt you can even list more than maybe 4 games where the devs/publishers added a gog-specific subtitle, so not exactly "always". "GOG edition" or "DRM-free edition" generally means "reduced functionality because we aren't really interested in removing Steam dependency and/or DRM". In fact, at least one such edition I know of was removed from gog because people saw through the ruse. Actually, given how often that happens in non-renamed games with no real indication thereof, it might be a good idea to add "GOG Edition" to at least every game on the 2nd class citizen list.

OP is half wrong and half right.

He's wrong that the issue he cites is GOG's fault.

But he's right that it's extremely misleading how the game is named "M" in order deliberately to fool people into thinking they are getting the real version, when actually they are getting the censored butchered gimped version instead.

How would M edition trick you into thinking you're getting AO version? They're two separate ratings, and less explicit isn't necessarily a bad thing or a reduced version. Just like there is a market for explocit materials, there is a market for less explicit versions. The dev made two versions with this in mind. I for one appreciate the option.

Geez, just read the store page about the game ffs.
"Lust from Beyond: M Edition is a new version of the cult survival horror Lust from Beyond. This edition is tailored to the preferences of players who love the genre of Lovecraftian horror for its mystery, narrative, and atmosphere rather than explicit content. "

If you're buying a game based solely on what the title is called, then you're being reckless with your money. This wouldn't "fool" someone who does a bit of due diligence, even by just reading the store page, before buying.

Basically two factor it legit is confirmed as the M meaning mature and edition usually in game terms mean a more complete and better version then a none ''edition'' game

If you have examples, feel free to post them! edit: Braggadar already posted the below info
Surprisingly, there's actually a section and decent explanation called "Changes in the M Edition" on the game page and not in small text, including "The original Lust from Beyond is an Adult Only experience."

I'd be fine with the original being released here, but as it is, they don't fool people into thinking this is the same version.