Digital Mars, makers of the C++ alternative D, have decided to discontinue the original version of D. They had been maintaining D1 along with its successor D2 since 2007, but with the later now well established they feel it is no longer appropriate to dedicate resources to the older language past December 2012.
In the announcement Andrei Alexandrescu writes,
Phasing D1 away will not only clarify our vision, but also free up considerable time to concentrate on D's two largest issues: (1) quality of compiler implementation and (2) breadth of the standard library. These two matters prevent users from fully tapping into all of D's core assets. They affect expressiveness because code that's supposed to work doesn't or necessitates ugly workarounds; they affect modeling power because bugs prevent full creative uses of the language, and lacuna in the standard library limit the "bricks" to use when building; and they affect efficiency because, evidently, a quality compiler and a good standard library are essential ingredients in writing efficient code.
D is distinguished by being C-like systems language with a much higher concern for safety. In addition to “const”, it supports declarations such as “pure”, “safe”, and “immutable” and by default only allows immutable objects to be shared between threads. As with most modern languages it disallows the reading of uninitialized values, has support for closures, and uses garbage collection to reduce the likelihood of memory leaks.