What does "stand-alone expansion" mean exactly?

Do you need the original game to run this or not?

No. It is more a spin-off game than an expansion. The ties to the original are quite loose, and it isn't required to run.

I played this game long ago borrowed from a friend and could never get my hands on my own copy. Thank you GOG for bringing us this old gem.

Trademarks are different from copyrights. Trademarks are used to prevent confusion in the marketplace. Trademarks automatically expire if they are not used or if the owner fails to renew the registration. The original 'Cataclysm' trademark expired on 4/4/2008 because of Section 8 - the owner let it lapse and it was cancelled. Blizzard registered 'Cataclysm' in two separate categories on 6/26/2009.

[EDIT] This only applies to registered trademarks in the US. There is also common law trademark which Homeworld: Cataclysm could still be protected by. It would be a viable defense against Blizzard in a court of law. Unfortunately it would also be a huge headache and is likely much easier just to change the name.

It's easy enough to see the original titlescreen again but I'm not sure if telling how would be allowed here.

As tremere110, touched upon in his post these things are all different things, being IP they have some overall, often superficial, similarities but there are lots of differences between the different categories:

Trademark, which can be registered or unregistered.
Copyrights, which can be registered or unregistered.
Trade secrets.
Patents.

You (generally at least) can't copyright individual words or phrases. You may be able to get trademark protection for them and if so you would be able to register said trademark. I am not sure about the exact priority rules when it comes to trademarks but in the US when you apply for a federal trademark registration with the USPTO, they do a search for products in your category(trademark is based around categories like for example entertainment, a trademark in one field doesn't automatically apply to other fields).

This search is in their databases, so that if there already is a registered trademark that is the same or "confusingly similar" in your field/category then you won't get to register your mark. I don't know but I think they may also do things like a Google search or something to see if there is already a prior product making use if the mark. After this process there is period where other companies might object to the USPTO granting the trademark if they feel they are the rightful owners of it since they were using it first in that particular category. So in this case, with Blizzard's Cataclysm trademark, Blizzard filed their trademark application on June 26, 2009 and it was published for opposition on September 15, 2009 and was finally registered on April 19, 2011. From what I can tell nobody(THQ included) objected to it. Actually it appears they have three such trademarks(in different categories, entainment, games etc). But the story is pretty much the same with all of them.

IMO trademarks are actually one of the least objectionable forms of IP. Accused of violating a trademark? Worst case scenario(usually at least) you change the name of your product, change your marketing slogan, change your logo or the like. Accused of violating a patent? Worst case scenario you go bankrupt. Accused of violating a copyright? Hypothetically you might even go to jail.

A case like this might be a reason to argue for reform to trademark law and/or to lobby Blizzard to change its practices, but is it a basis for arguing for abolishing trademarks? That is very doubtful.

You don't need the original, hence "stand-alone".

The way I see the term, it means a game which probably uses the same engine as the "main game", has similar gameplay idea, and is smaller in size. And like in this case, it probably started as an expansion (which would need the main game), but at some point they decided maybe it should be a separate game altogether.

So basically, usually more of the same, and don't expect a new game engine or be as big the game as the previous one. In a way though, it is a meaningless term. (Then again people do say that Cataclysm/Emergence gameplay differs from the first Homeworld, so...).

So it's all the same except for the GOG release? Title screen, manual, it's all cataclismic-ish!? :P

The Tools folder allows to change to higher resolution. That's nice.

Not trying to be a pain but is it the most expensive classic release to date? ;)

Try as a might I can not get this to work on my rig. I did the reg hack and tried all combos. The best I can get is 640 x 480. Its confusing as do you use the glide config and the hack together? Too many possible combo's!

Btw GOG, on the game description page you use the word "Hilgaran"...it should be "Hiigaran" with two i's, not an i and an L :)

Make sure to run the game as administrator.

Uh-uh. If you say so with that apparent need of sounding a likable person, then it must be true. *POP*
Something tells me though that an enforced monopoly on behalf of a certain company is still capitalism. Because, you know... states are capitalists, too. It's not like the two things are somehow magically divided: once you choose an economic model (as a sovereign state) you partake in that economic model.