A few points about the item you linked to:
1. This is an arrangement for 2 trumpets and organ made by someone other than Holst. The arrangement could easily be under copyright.
2. Even if the arrangement referenced above was made by someone who died before 1962 and was first published before 1923, the linked score is a recent typeset or edition and therefore not postable here without the editor or typesetter's written permission or sufficient evidence that the edition was released under a creative commons or similar free license.
3. Fortunately, the words are by an author who is public domain in most of the world - Cecil Spring-Rice (1859-1918)
. If Spring-Rice had lived until 1949, the text would still be under copyright in the EU and other 70 pma countries. This is a good illustration of how even a well-known work has more than one contributor. Holst (1874-1934) took his own tune from the "Jupiter" movement of The Planets
and adapted it to Spring-Rice's text. This arrangement - for unison voices and orchestra - was probably first performed at a commemorative service in 1921 and published by Curwen in 1921 or 1922 (along with Parry's Jerusalem
4. Host expanded and reworked the piece into a hymn entitled "Thaxted" later for inclusion in the collection Songs of Praise
, edited by his friend Ralph Vaughan Williams. This collection was first published in 1926 and could be protected in the USA until 2022 - including the "Thaxted" arrangement.