The MusicBrainz Client Library (libmusicbrainz), also known as
mb_client, is a development library geared towards developers who wish
to add MusicBrainz lookup capabilities to their applications.

Note: Version 5.x and greater support the latest version of the
MusicBrainz web service and are not backwards compatible with earlier
versions. As of 2011, version 3.x and below have been deprecated.

It is safe to have versions 2.x, 3.x, and 5.x on the same system as
they don't conflict with each other.