libmusicbrainz should be ported to use NSS library for cryptography. See the tracking bug for details and links on how it could be done.
libmusicbrainz doesn't use any cryptography. The development version of libmusicbrainz will use neon in the future. That's where the crypto should be ported.
It contains its own SHA1 implementation. Although if it is not used for security relevant purposes then it doesn't matter much to this project. On the other hand the code duplication should be avoided.