This is v2.1 of a Basic Interpreter by Phil J. A. Cockcroft earlier versions used to be known as Rabbit Basic.

According to an earlier licensing document:

=== This code is being put in the Public Domain since I will soon loose network connectivity (I am leaving my job) and I don't particularly want to sell it. This system does not contain any proprietary software. All the algorithms are original or come from publicly available sources.

There are no licensing restrictions on this code or documentation at all. I only ask that you give appropriate credit to the author.

So, there you have it. :)