Dimensional Developments was a research company.
It was part of the maze surrounding Veidt Enterprises. It funded the Institute for Extraspatial Studies. In turn, it was funded by Pyramid Deliveries.[1] Veidt financed DD with the proceeds of the spark hydrants he developed.[2]
Dr. Mahattan's past associates, Janey Slater, Wally Weaver were employees of the firm. All of them were unwittingly exposed to radiation and later suffered cancer. They were used as part of a plan by Veidt to get rid of Dr. Manhattan.[1][2][3]
Following this plan, when Moloch got out from prison, Adrian Veidt offered him a temporary job, presenting him a chance to atone himself from his past life. He worked in an enclosed office comparing and cross-checking the results from research teams testing a new energy source. He didn't know that Veidt introduced some errors himself to check if Moloch could detect them. Veidt had hid a radioactive source in his office in order to cause cancer to him.[4]
Dimensional Developments apparently did all the research concerning teleportation, ultimately triggering the Alien Monster.