I've noticed that some apps trigger a login prompt when you add them from the SharePoint Store. From what I can tell this seems to be due to some applications requiring authorisation of a Microsoft ID (thus your Office 365 account simply doesn't cut it). Apparently this is merely to trigger the installation, and afterwards the application won't be correlated to your private account.
My question is whether anyone knows why exactly it needs a Microsoft ID for authorisation if it's basically doing nothing with it beyond the install?
I'd also like to know if there's any workaround to this issue as I'd prefer to not have this linked to my personal account, nor have to setup more accounts to keep track of for administrating the SharePoint domain.