Or you take Les heures gregoriennes - which are, AFAIK, not up to date with the current Ordo cantus officii, and don't contain the Office of Readings.
56. Libri cantus liturgici Ecclesiae Romanae hucusque typice editi sunt:
Graduale Romanum, cum Ordinario Missae.
Antiphonale Romanum pro Horis diurnis.
Officium Defunctorum, Maioris hebdomadae et Nativitatis D. N. Iesu Christi.
Im not sure about the legality details, but i would insist that the intention of the compiling author is more important than formality issues. (Spirit of the law rather than letter of the law)
Once the author is dead, not only he and his work, but also his heirs must be taken into account. Sandhofe lived in an era when the spirit of free opensource software and other free (libre) content was already well established, but he didn't opt to operate this way, which definitely has something to say on "the intention of the compiling author".
The impression that the nocturnale of the Vatican basilica receives from the https://nocturnale.marteo.fr/ folks less love than Sandhofe seems to be correct. I'm not sure if this is a principial decision or if it's more about how familiar they are with each of these publications, how much of their contents was readily available at GregoBase etc.
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