Compiling DTDs - highsource/jaxb-tools GitHub Wiki
If you want to compile DTD, change the schemaLanguage to DTD and set the appropriate schemaIncludes:
<configuration>
<schemaLanguage>DTD</schemaLanguage>
<schemaIncludes>
<include>*.dtd</include>
</schemaIncludes>
</configuration>See the sample DTD project for example.