I just visited Impulse's homepage and was immediately reminded of GOG.com's homepage. Imitation is the sincerest form of flattery? ;)

The layout is more than a bit familiar, isn't it?

Oh.. they changed it..
I have to admit some similarities with GOG.
...
Ok.. it's a damn carbon copy.

Hey... it does! From the sidebar to the fancy lightbox on the front page to the links and search bar on the top! Even the news section is exactly where GOG puts theirs on the front page!
Ooh, reminds me, I must remember to update my Impulse client.

Indeed, there is a strange resemblance... :)

Ugh...white backgrounds... =_=

Yes it does show more than a few similarities, the white background is a little stark though.

That was my reaction too.

Similarities are quite high
I would take a guess that there was a basic site template both places used to create their layout. But a copy is always possible, even if unintentional.

I find it unlikely that the good people at Stardock have never seen GOG's website. It might be a common (yet underused, considering it's awesomeness) template, but even then there's no way they could have failed to realize GOG used it as well.

I highly doubt that either company bought some cheap template for their site.
Even if that was the case, would that explain why Impulse's upcoming games are in exactly the same place as GOG's?

If the source was the same, or close enough then yes. A container waiting to draw data from someplace, but in this case, it's the same location and same type of data.
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There are only so many basic layouts you can do, minor differences aside, and similarities are going to show eventually. But this is all speculation really.

Even if there was a template and it was... rather specific, Impulse should be well aware of the competition and should avoid appearing to be a clone of an existing service.

I can't disagree with that.

Yeah.. I'm quite puzzled by this, actually.