> However, it doesn't make any sense to do that to cultural artifacts created by citizens a colonial power in their own originating culture.

The issue here is that these works have been in a private library, inaccessible to the public, since the 1930s.

In this case, the author is using "decolonize" to mean to liberate the work from private ownership and make it available to the public.

When "decolonize" is used in the context of e.g. education, it refers to restructuring an education system to be more equitable to all students. As such, the idea of providing access to everyone is a default implication of the term, even if its origin more specifically relates to dismantling the colonial baggage that led to structural inequality.