As pointed out elsewhere, the grunts in Aliens were not "space marines". Once again: this is a trademark. GW doesn't have a monopoly on the idea of "Sci-Fi Marines". They have a trademark on the specific term "Space Marine" as used within their realms of business. That includes fiction, so the linked post was infringing. Sorry, but it was.
Arrgh. AGAIN: it's not a patent! "Prior art" proves nothing. If this figure's manufacturer was not a going business venture in 1987 (or whenever GW filed that trademark) then GW was entirely within their rights to file such a trademark.
And even if this was 100% contemporaneous, the party with standing to challenge that trademark would be the toy company, and not the linked post. The remedy would be to immunize the toy company from GW, or perhaps to award them damages due to GW's mark causing loss of sales.
He's not claiming that their trademark is invalid because of "prior art", he is saying that they should not have a trademark on the term in the same way that Tropicana should not be permitted to have a trademark on "orange juice".
That is to say, "space marine" and "orange juice" are both clearly descriptive marks. That "space marine" is a descriptive mark is evidenced by it's long history of usage.
The article says GW is claiming an implicit or common law trademark rather than a registered one. The rules for that are far more grounded in equity than the rule based statutory system.
Edit: that is to say the expansion into the book market is a common law extension. To be clear the mark was registered in the game market.
As other people have pointed out, in the United States, GW's trademark for "Space Marines" does not include fiction in their "realms of business." So this is extremely dubious on its face.
Furthermore, under UK law, a trademark can be invalidated on "absolute grounds" which "cover defects in the trade mark itself":
The most common absolute ground for invalidation is that the trade mark is descriptive of the registered goods and/or services, or that it is generic for those goods/services, or otherwise non-distinctive and should therefore be free for everyone to use.
And, actually, according to that law, anyone can apply to have the mark declared invalid on absolute grounds.
The underlying issue at hand -- and this applies to American law as well -- isn't precisely about "prior art." It's about whether the phrase "space marine" is already too generic for the trademark to hold, especially when applied to fiction. "Marine" certainly isn't a GW trademark; this whole claim is predicated on the notion that it becomes uniquely theirs when the word "space" is put in front of it.
...so the linked post was infringing. Sorry, but it was.
That's not the question, is it? The question is whether it should be infringing.
http://www.imdb.com/title/tt0090605/
I'd personally been using the term since growing up watching Star Blazers cartoons in the 70s.