The plugin may also be found here http://www.zenphoto.org/2008/06/zenphoto-plugins/#spamfilter-akismet. If you will provide your changed version, we will update the site with it. Thanks for letting us know it still works on 1.2.5. Some others had had issues with earlier Zenphoto versions.
You can create a ticket and attach your updated file. Maybe we can even fix the install instructions