Comment by gtrubetskoy

Subinterpreters existed from the very early days in the C API and were key to the implementation of mod_python (which I wrote). So if you used mod_python, you used subinterpeters without realizing it.

http://modpython.org/live/current/doc-html/pythonapi.html#mu...

EDIT: And it looks like I had subinterpreters in the first released version in May 2000, so the initial git (formerly SVN) commit already had them https://github.com/grisha/mod_python/blob/9b211b7e8a65f1af4b...

EDIT2: Just noticed this comment:

  * Nov 1998 - support for multiple interpreters introduced.