It's basically as simple as it sounds. It's a PC emulator, and Libretro (the housing for Retroarch) calls it a potential rival to DOSbox.

• Have any of you actually used this? How is it?

• Might this be useful to GOG if they could obtain an agreement? Might it open the realm for more obscure games and niche titles like Odell Lake?

•And does it rival BosDox?

It's open source, so an "agreement" mightn't be necessary. As for using it, I haven't had the pleasure. DOSBox is still in development, even though there hasn't been an official release for a couple of years.

Edit: After a bit more reading, it doesn't actually aim to replace DOSBox. Its purpose is much broader in scope; emulating entire machines from our computing past. This seems unnecessary when considering GOG games, unless there are titles here that have issues with DOSBox?

Which there are a handful. Not to mention, there's good games on other systems. Like the Apple II, but wouldn't you need a boot file?

The Bard's Tale (200X) contains emulated versions of the original trilogy. For 1 and 2, the Apple IIgs versions are used, while 3 uses the Apple II version. So yes, there is a game containing an emulated Apple II game.

Note that the Apple II version of Bard's Tale 3 is one of the good versions, unlike the rather buggy DOS version. (I hope the remaster will not have the DOS version's bugs.)

Were there any bug enemies in The Bard's Tale?

I seem to remember there being spiders in at least Bard's Tale 2, maybe 3 as well.

Arachnids don't count. :V

first time i heard of it

I understand, it is something I only recently heard of too.

Thanks for this, I'll check it out.

might be interesting to check out all the same though

Never heard of it before. I may use it.

I used it a lot while I was on Windowz, but haven't really used it since switching to Linux. I doubt it, as it needs Bios roms & OS to run, so using it commercially GOG might run into problems with MS and whichever Bios Company the bios you use comes from. I thing they not rivals, DosBOX is aimed to dive a basic environment for you to play old dosgames without any thought to the underlying emu. PCeM is more a preservation of computers from yesteryear. I think there is about the same difference between DosBOX and PCem as what the Difference is between DosBOX and MESS/MAME (no that MeSS was swallowed by MAME)

How I differentiate between the two:
DosBox: it's a Dos Box (Simulator)
PCeM: It's a PC Emulator

Looks like you can just choose your hardware, boot into the black void and install any OS that works. That's really impressive. I've had a lot of fun playing around with Mac emulators like Basilisk II and SheepShaver, and I've always wished there were similar solutions for Windows 9x.

Edited:
Or to put it another way:

DOSBox emulates a specific software/hardware environment.

PCeM emulates a range of specific hardware environments.