This soundtrack is listed as 'enclosure'. Did this come with the game? Unfortunately, there is only little information for the game on the internet.
What made me wonder is that
ZIZZ STUDIO's discography lists an official CD+DVD release for the same date (2001.04.29).
Apart from that,
Nitroplus' shop and
HOBiRECORDS list the soundtrack under the catalog number 'NTRSUN-003', indicating that it's an official release.
I could also find an
auction that says that there are 2 discs and since the cover matches the one we have
here (note the 'DVD'), this entry might be actually for the official soundtrack.
It's seems also possible to purchase it via
amazon.co.jp.
EDIT: I finally found some pictures of the content for this soundtrack and it does include the mentioned DVD. (
disc 1,
disc 2) I think there is enough evidence prooving that this is actually the entry for the official release so I made some changes to the entry including adding the catalog-number (there is no cat-no printed on the release, not even on the obi), JAN and DVD medium with corresponding tracklist.