Price doesn't determine it... Steam copies include achievements, at the least, which has to utilize agsteam.dll* .. Therefore developers typically have a build that's separate from the main or "DRM-free" version. This is the same for any game on Steam made in AGS that has to in some way, utilize something the Steam client does. There's additional code in the build. Of course, it's quite possible to put the game up sans Steam code, but that isn't the case here, nor with many AGS games that have a build on Steam.
The flip side of course, is whether someone is distributing the Steam-code version as their main/DRM-free version. It can and generally will work, but that's still a bit of a distribution boo-boo. It's best to keep the steam code and files out of that copy. That said, it's an understandable oversight even I've made it in the past. You won't find many discussions on the boards about it, and it's only in recent years I've explicitly split my builds up to the 2 forms, but from here on, I'd always say it's best to keep your Steam version for Steam and leave the files and code out for your internet download version.
So, you mention having it from Crystal Shard's website but still have an issue? It sounds like Radiant perhaps has up the Steam build as his DRM-free version. I'm not sure what the copy on my site has (screen7.uk > free) version 1.2.1, maybe Radiant knows about this error or at least, can point you to a build which doesn't have Steam code or the dll in it (and me please!!).
* I wonder, is this meant to mean "AGS Team" or "AGS Steam" (with spelling error) ? or "AG Steam" ? It's been bugging me for years

All of that said, agsteam.dll isn't part of the installation. It is utilized when you run the game. So if you're having this issue during installation itself, it might be something else entirely? If it seems to mostly install, it's often worth trying the "Verify Integrity Of Game Files" in properties > local files in Steam, which should detect an inconsistent installation and try to re-acquire the problem file(s). Though it sounds like you're trying to play it without Steam, so outside of Steam, it could be an issue down to whomever created an installation file for it?