Public domain is a nice (lack of) license, in principle. In practise, though, that is only the case in the US and other areas with similar copyright laws. For example, in German and Austrian law it is not possible to disclaim copyright and therefore anything licensed under public domain falls back to "all rights reserved".
Would you consider changing the license to something equally permissive, such as the MIT license? It also has a warranty disclaimer, which may not be a bad idea for software.