Smalltalk is an object-oriented, dynamically typed, reflective programming language. Smalltalk was created as the language to underpin the "new world" of computing exemplified by "human–computer symbiosis."It was designed and created in part for educational use, more so for constructionist learning, at Xerox PARC by Alan Kay, Dan Ingalls, Adele Goldberg, Ted Kaehler, Scott Wallace, and others during the 1970s, influenced by Lisp, Logo, Sketchpad and Simula.
The language was first generally released as Smalltalk-80 and has been widely used since. Smalltalk-like languages are in continuing active development, and have gathered loyal communities of users around them. ANSI Smalltalk was ratified in 1998 and represents the standard version of Smalltalk.

If languages are defined by standards, what makes them open source? Well, the specification itself can be proprietary. You'll find in older main frame languages if you wanted the specifications you had to pay huge amounts of money for the detailed specifications.

The second opportunity is the implementation itself. For example with Ruby, there are several implementations, all of them happen to be open source.