You only need to register and the games will appear in your library. It wasn’t clear when the giveaway will end, only that it will end once their contract ends. https://i.imgur.com/wZW6Hvo.png
Edit: Seems like they’re giving these before they delist them. From their Discord:
Dear All,
Ziggurat Interactive has demanded that we take Killing Time as well as all Majesco titles down and strongly requested we pay all royalties due. Despite the fact that we had legal and valid contracts. As many of you already know, we have fought this battle for sometime. Beginning with converting Killing Time (July 22nd 2015), a feat deemed impossible by GOG, and subsequently having the code we created misappropriated (March 2016). It’s amazing how that title has jumped from Tommo to Retroism to Ziggurat…
Now, while we were given the option to overprice our titles and keep royalties…We said NO. It’s not about the money. It’s about our users. So, as a parting gift, please find the following titles added to your account as part of our contract expiration promotion: A Boy and His Blob, Advent Rising, BloodRayne, BloodRayne 2, BloodRayne: Betrayal and Killing Time
Yip. That was it. Six titles added. Miss Rayne seems interesting. Never heard of them before, that site. Thanks @carvalho20ptc and @SeekerSupreme You two know all the deals.