I believe these need a leading slash, as below:
```
RewriteRule ^/en-US/firefox/releases/1\.(.*)$ http://website-archive.mozilla.org/www.mozilla.org/firefox_releasenotes/en-US/firefox/releases/1.$1 [L,R=301]
RewriteRule ^/en-US/firefox/releases/0\.(.*)$ http://website-archive.mozilla.org/www.mozilla.org/firefox_releasenotes/en-US/firefox/releases/0.$1 [L,R=301]
```