Retro is a concatenative, stack based language with roots in Forth.
It is designed to be small, easily learned, and easily modified to meet specific needs, it has been developed and refined through continual use by a small community over the last decade.
The current release series. This has focused on providing a cleaner, stable language, with a richer set of libraries and better documentation. It's still under active development and will remain so for the foreseeable future.
After the 9.x release series ended, I rewrote Retro for use with a portable virtual machine. This was done to address some design issues, and to reduce the support headache of trying to maintain a cross-platform assembly codebase.
10.3 was significant because we started using a metacompiler, rebuilding the Retro image using only Retro from then on. 10.5 brought files, vocabularies, and a change to the VM to improve code density. The 10.7.x releases were done to bridge the gap to the 11.x release series.
The 9.x releases were generally good. They continued to be written in x86 assembly, and reached a stable status. Additionally, thanks to Neal Bridges, 9.2 included optional support for most of the ANS FORTH specification.
The 8.x releases brought the assembly language implementation to its most portable point. We supported multiple operating systems and could leverage the standard C library for portability to systems not officially supported.
These releases were where Retro started gaining a following. It also saw the beginning of a serious effort to provide portability in the assembly codebase.
There were a lot of releases during the 6.x days. The code moved from running only on raw hardware to being usable under Linuxi, Windows, and FreeBSD.