It is now possible to share all new or already made SongBook + in-app purchases (full version or sponsorship, whether subscription or 5-year purchase) via the family share.
The prerequisite is that family sharing has already been set up for the Apple ID's belonging to the family.
You can then enable family sharing for specific subscriptions. There is no separate approval to share the 5-year purchase of SongBook; the general approval for in-app purchases applies here.
For subscriptions:
To do this, press in the AppStore app on the top on the Apple iD, then "Subscriptions" and then on the corresponding SongBook subscription. In the subscription there is then a switch "Share with family", turn it on.
For 5 year purchase:
To do this, press in the general settings of the iPad / iPhone on the Apple iD, then "Family sharing" and "Share purchases". There is then the switch "Share purchases with family".
After setting up the share, it may be necessary to call up the "Restore in-app purchases" function in SongBook + on the affected devices so that SongBook + notices the change.
See also here for more information: https://apps.apple.com/us/story/id1542695115