Question regarding source files with unclear license

Hi,

I was working on updating the dap-mode package[1] (team repo[2]) and
noticed that the previous maintainer removed some of the source files
stating that they have unclear license[3].  If you look at those files,
for the text files they don't really have a copyright header, though I
would expect that those files should be under the common license by
default (which is GPL-3[4]).  There are also some binary icon files that
are used as control.  It includes vscode icons[5] which seems to derive
from this upstream repo[6] with CC BY 4.0, and eclipse icons[7] which
seems to derive from this upstream repo[8] with EPL-1.0, and both
licenses are DFSG-compliant.  Admittedly the dap-mode upstream could be
a bit clearer about the license on those icons by providing a dedicated
license file under those directories, and I can file a PR upstream to
request that if needed.

OTOH, AIUI, the removal of those files was not required for the package
to be considered DFSG safe as all licenses seem to be DFSG-compliant
(also the previous maintainer didn't mark the package version with any
"+dfsg" suffix after removing those files).  On the other hand, removing
files results in difference between upstream source, and this could
potential cause packaging issues when upgrading to newer versions
(e.g. newly added files may depend on files that were removed).

I wonder whether those removed files should be considered with unclear
license, and if not, whether I can add those files back.  Hence I would
like to consult the debian-legal@ folks to make sure things are indeed
DFSG-compliant.

TIA!

[1] https://tracker.debian.org/pkg/dap-mode
[2] https://salsa.debian.org/emacsen-team/dap-mode
[3] https://salsa.debian.org/emacsen-team/dap-mode/-/commit/e227c8dc6ab6c3f2b932a5605838548bd3f16cbc
[4] https://salsa.debian.org/emacsen-team/dap-mode/-/blob/master/LICENSE?ref_type=heads
[5] https://github.com/emacs-lsp/dap-mode/tree/master/icons/vscode
[6] https://github.com/microsoft/vscode-icons
[7] https://github.com/emacs-lsp/dap-mode/tree/master/icons/eclipse
[8] https://github.com/eclipse-platform/eclipse.platform.images

-- 
Regards,
Xiyue Deng

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