While the EFDSS is the main source of funding, I think "quasi-autonomous" might be nearer the mark. There's a potted history in the VWML link I gave earlier in which it is explained:

Funding

VWML is funded and maintained by the English Folk Dance and Song Society, with additional support from the Ralph Vaughan Williams Trust, the National Folk Music Fund and many individual members and clubs. If you would like to help develop and promote the work of the Library you could:

join the EFDSS, finance a project, publication or event*, buy a book or sound recording, donate or bequeath funds or material to the Library*, donate or bequeath funds to the National Folk Music Fund*.