about 1 years ago, j became FOSS.
The J programming language, developed in the early 1990s by Kenneth E. Iverson and Roger Hui, is a synthesis of APL (also by Iverson) and the FP and FL function-level languages created by John Backus.
J is not a von Neumann programming language; however, it is possible to use the von Neumann programming style.
Since March 2011, J is free and open source software under the GPLv3 license. One may also purchase source for commercial use under a negotiated license.