This system is sometimes referred to as kbasic or kidbasic instead of basic256.

Upstream development uses svn. This can be checked out directly with

   svn checkout https://svn.code.sf.net/p/kidbasic/code/trunk basic256-svn

or using git with

   git svn clone https://svn.code.sf.net/p/kidbasic/code basic256-svn --stdlayout

or yanked into an existing git repository

   git config --local svn-remote.svn.url 'https://svn.code.sf.net/p/kidbasic/code'
   git config --local svn-remote.svn.fetch 'trunk:refs/remotes/sf/trunk'
   git config --local svn-remote.svn.branches 'branches/*:refs/remotes/sf/*'
   git config --local svn-remote.svn.tags 'tags/*:refs/remotes/sf/tags/*'

   git svn fetch

These are the upstream discussion forums; the first of these seems abandoned.

   https://sourceforge.net/p/kidbasic/mailman/kidbasic-devel/
   https://sourceforge.net/p/kidbasic/discussion/

 -- Barak A. Pearlmutter <bap@debian.org>, Thu, 29 Oct 2020 10:19:51 +0000
