Games in the giveaway list with stars next to them?

Whilst going through the giveaway list, I saw a few games had stars next to them.

Eg: Here

Any specific reason? These games aren't in the "Keys Considered Exploited" list, and the star is not mentioned in the FAQ page.

I wish to make a giveaway of one of these starred games (Specifically Space Pirates and Zombies) and was wondering if this was allowed.

Thanks \o/

Edit

It turned out SPAZ was previously in a bundle so would give me reduced contributor value as per these posts. Fine by me! \o/

Thanks to those who helped :)