With respect to the supported versions, "support" constitutes a promise to address security-related bugs by applying patches to the subversion branch. It may include additional formal releases to incorporate these fixes, but this is NOT guaranteed. Other bug fixes and enhancements are likely to be restricted to issues that impact our ability to continue to support the 1.3.x branch of the Shibboleth code base. Other issues are likely to be ignored.
As far as informal support is concerned, at this stage, very few non-trivial questions are likely to be addressed promptly, if at all. If this is a concern, you should seriously consider planning to migrate your code to OpenSAML 2, or consider a more well-supported library. This is simply a function of the original author's time (or lack thereof) to support this older code.
Finally, our willingness to support this library branch at all is tied to our support of the Shibboleth 1.3.x code base. If at any time, we schedule an EOL date for either the Shibboleth IdP or SP releases on the 1.3 branch, the same EOL date will apply to the legacy OpenSAML branch. We will send a notification to the OpenSAML mailing list at that time.