"Cholera" from THE PAINTED VEIL, with the electric cello arpeggios, is also unmistakably Glass-like. My bet would be homage, and as for THE GRAND BUDAPEST HOTEL, I haven't stopped listening to it for the past week. A masterpiece.
Pretty much any composer who has written music since Philip Glass could be accused of "copying" him, just as he could be accused of "copying" most of the composers who've come before him.
But it's because Glass has always based his music quite consciously on elementary musical materials - both in terms of notes/chords/arpeggios and in terms of rhythm. So it's as if the skeletal structure of Glass's music is the skeletal structure of just about all major classical and orchestral music.
It's what's built on the skeleton that makes the difference. Glass's builds on the structure with repetition, layering of multiple scales/chords/rhythms and so on, and that's what creates the distinctiveness of his sound.
And Desplat has certainly incorporated many of those minimal principles into his work, but beyond the idiom and the occasional sharing of particular patterns, Desplat doesn't sound like Glass in any fundamental way. And I think these two clips are actually good examples of the difference between the two using similar starting points.