db4o is an object database for Java and all .NET environments. Its features include ACID transactions, automatic class schema recognition, query-by-example, a S.O.D.A. object querying API, native queries, LINQ support on .NET, callback methods, memory files, cascade-on-delete, multi-threaded access, and Java Webstart and servlet support.
dbtcp is a package of libraries which provides applications on Linux access to ODBC datasources on remote machines running Windows. It allows a Linux application to access data held on a Windows machine (such as MS SQL Server on NT), and includes a command line client, a DBD, and a PHP driver.
DeleGate is a multi-purpose application level gateway or proxy server that mediates communication of various protocols, applying cache and conversion for mediated data, controlling access from clients, and routing toward servers. It translates protocols between clients and servers, converting between IPv4 and IPv6, applying SSL (TLS) to arbitrary protocols, merging several servers into a single server view with aliasing and filtering. It can be used as a simple origin server for some protocols (HTTP, FTP, and NNTP).
DeuTex is a wad composer for Doom, Heretic, Hexen and Strife. It can be used to extract the lumps of a wad and save them as individual files. Conversely, it can also build a wad from separate files. When extracting a lump to a file, it does not just copy the raw data, it converts it to an appropriate format (such as PPM for graphics, .au for samples, etc.). When it reads files for inclusion in pwads, it does the necessary reciprocal conversions. In addition, DeuTex has functions such as merging wads, etc.
dopewars is a UNIX rewrite of the MS-DOS program of the same name, which in turn was inspired by John E. Dell's "Drug Wars" game. You have one month to buy and sell drugs on the streets of New York, the aim being first to pay off your debt to the loan shark and then to make a fortune. And if you have to shoot a few cops in the process, well... The game includes TCP networking allowing you to meet (and shoot) other human drug dealers. Computer drug dealers are currently in development.