The sale covers Duke Nukem (1991) and Duke Nukem 2 (1993), which are sold together in a package; Duke Nukem 3D Atomic Edition (1996); the pinball spinoff Balls of Steel (1997); and Duke Nukem: Manhattan Project (2002). They regularly cost $5.99 each but are on sale for $1.49, 75 percent off. However, if you buy all of them together, you'll get them for just $2.36, a discount of 90 percent.
GOG.com will be running the sale until 5:59 a.m. ET on Thursday, Dec. 31, at which point the five games will disappear from the service. That's because the listed publisher, 3D Realms, no longer owns the rights to any Duke Nukem games. In the settlement this past August of the intellectual property lawsuit between 3D Realms, Interceptor Entertainment and Gearbox Software regarding Interceptor's Duke Nukem: Mass Destruction, Gearbox claimed the full rights to the Duke Nukem brand.
As for the Duke Nukem games that are leaving GOG.com this Thursday, the retailer said, "We are in talks with the new rightsholders to bring them back as swiftly as possible." A representative for GOG.com confirmed to Polygon that Gearbox is the company in question. The blog post from GOG.com noted that anybody who already owns any of the games at the time of delisting will not see the titles disappear from their library.
The GOG.com versions of Duke Nukem, Duke Nukem 2 and Duke Nukem 3D Atomic Edition are available on Linux, Mac and Windows PC. Duke Nukem: Manhattan Project supports Mac and Windows, while Balls of Steel only runs on Windows.