I would guess the same.
These predated our move to GitHub. I agree that it would make sense to manage them within openmrs-core (they’d still need to be hosted at resources.openmrs.org/doctypes).
If we can identify the differences from 1.5 to 1.6 in config.xml, I can create the DTD if needed.
BTW… the existing DTDs appear to have undeclared elements (for example, in 1.4 and I think 1.5 is the same, I see these as undeclared: class, point, mappingFiles, allow, init, signatures, filter-class, filter-name, servlet-name, url-pattern, defaultValue, description, property, param-name, param-value, file, lang, activator, author, id, name, package, require_database_version, require_version, updateURL, version, servlet-class). We also have a pretty ugly history of naming conventions combining under_score, hyphen-ated, and camelCase.