A client for gepro-osi schools (specifically tailored for school 507), the private api is yet to be open-sourced (if at all).
The private API is currently unpublished and can be bought for a negotiatable price. You can contact me on [email protected] if you're interested. (The same goes for the domain norbertaan.nl as well).
A lot of stuff is set up to use my accounts (such as analytics or notifications), this is OK for you to use but keep in mind that you won't be able to tweak the settings. (Or do anything for that matter.)