The source contains a BCP78-licensed [1] test data [2], referenced by an example and a few tests.
I don't feel comfortable navigating legal topics (for now, being a new Debian contributor), so instead I asked the upstream [3] and a fork [4] if they could find an alternative test file.
I have purged the source repo [5] and will park this ITP for now. Feel free to pick up.
[1] https://www.rfc-editor.org/info/rfc4511/
[2] https://github.com/eerimoq/asn1tools/blob/master/tests/files/ietf/rfc4511.asn
[3] https://github.com/eerimoq/asn1tools/issues/203
[4] https://github.com/boxtheta/asn1tools-ext/issues/4
[5] https://salsa.debian.org/python-team/packages/python-asn1tools/