/usr/share/openmsx/softwaredb1.dtd is in openmsx-data 0.10.0-1ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 | <!ELEMENT softwaredb (person*)>
<!ELEMENT software (title, genmsxid?, system, company,year,country,dump)>
<!ELEMENT title (#PCDATA)>
<!ELEMENT genmsxid (#PCDATA)>
<!ELEMENT system (#PCDATA)>
<!ELEMENT company (#PCDATA)>
<!ELEMENT year (#PCDATA)>
<!ELEMENT country (#PCDATA)>
<!ELEMENT dump (#PCDATA)>
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