Blender release life cycle and versioning I was trying some older versions but version numbers and release versions are not clear to me.

For instance how can I know what is the most stable release of a given version, say 2.49:

The folder listing looks like this:

...
Blender2.49/    2009-Jun-04 09:24:18    -   Directory
Blender2.49a/   2011-Jul-11 16:08:09    -   Directory
Blender2.49b/   2009-Sep-16 09:53:26    -   Directory
...


So, which one is the stable release, is it the "newest one"?, so what does the letter a stand for, is it alpha?

How is it related with the software release life cycle common acceptance?
AFAIK, the letter doesn't stand for anything. It is appended to the version number when there is a bug fix release with minor changes after the initial release, and incremented with subsequent bug fix releases. So 2.49b is the latest version of 2.49.

The date refers to the last time the directory or file on the server was modified: