This site is called Duke3D Online and you can download the program called "Meltdown" to play 4 Build Engine games with ports or dosbox like Duke Nukem 3D, Blood, Shadow Warrior and Redneck Rampage.
When you are installing the program to your computer, it will ask you about to install only the program or install the program and download the games that you choose. If you choose to install the program and download some or all games, the program will download the games in full version, and all their stuff (full version games, mods, expansions, levels, editors, ports, dosbox, tools, etc) like 1.47gb of all 4 games stuff with all to play online. Try it
link:
http://duke3donline.com/Players/index.php