From my perspective, it's fine to archive the copy of gspell in GNOME's GitLab.
FWIW I do not agree. We have several active projects depending on gspell:
elements/core/evince.bst:- core-deps/gspell.bst
elements/core/gedit.bst:- core-deps/gspell.bst
elements/core/gnome-builder.bst:- core-deps/gspell.bst
elements/core/gnome-software.bst:- core-deps/gspell.bst
elements/world/evolution.bst:- core-deps/gspell.bst
elements/world/geary.bst:- core-deps/gspell.bst
elements/world/gitg.bst:- core-deps/gspell.bst
elements/world/gnome-recipes.bst:- core-deps/gspell.bst
This is not going to be so easy to roll back like it was for tepl and amtk. These dependencies need to be dropped before the repo is archived.
P.S. I'm still waiting for an explanation as to what happened to your other projects in #564 (comment 1086095).