The 0.4 branch was an internal development version, where experimentation for security fixes happened.
Security flaw release. Contained no fixes, rather removed all vulnerable features. Intended for (limited) continued use while fixes were being performed.
May 12th, 2005 
- ".tld" support in @include/@exclude, allowing things like
@include http://www.example.tld/for all international permutations.
- Log level option for GM_log
- Minor enhancements and bugfixes.
Primarily bugfix release.
- Edit button in the manage dialog.
- Monkey icon in the status bar, click to enable/disable.
- GM_getValue, GM_setValue, GM_log
Also, the default user scripts that were bundled with Greasemonkey by default until this point were removed.