At risk of going off-topic to reply (sorry - let's get back on topic after this!):
Most importantly, Bing Maps licence doesn't allow their maps to be stored and used offline.
Links e.g.
https://social.msdn.microsoft.com/Forums/en-US/f7cd7920-2582-47be-9244-8151f72b9be5/bing-map-licence-for-offline-use?forum=bingmapsservices (note very clear answer marked by Ricky Brundritt who is Bing Maps head honcho) or
https://stackoverflow.com/questions/6326120/bing-map-offline-development-is-this-possible The important bit of the terms you agreed to when you signed up for a Bing licence is that
"[you may not] Copy, store, archive, or create a database of Content".
Offline use relies on storing maps. Otherwise, why do you think other apps don't just do this? Getting each user to take on their own licence makes it difficult to deal for Bing to deal with as I'd mentioned above.
OS (and presumably other mapping providers) have different licences for offline use, which are much more expensive (as online fees are payable over and over each and every time you look at the map, hence must be cheaper). That's the same as our licence.
Beyond that, definitions from Bing Maps licence terms for use in non-profit app:
Education or non-profit organization use. If you are using the Services with an Application that displays results for Education or Non-Profit use, then your Application must be one of the following: (i) publicly available without restriction (for example, login or password must not be required); (ii) available only to current students of your educational organization via your private network in order to provide education-related services; or (iii) available internally for free instructional use or available internally for non-commercial research use. Commercially-funded research projects and commercial company use for educational purposes are excluded from Education and Non-Profit use. "Non-profit" means a tax exempt organization. "Education" means use by public or private K-12 schools, universities, community colleges, or other collegiate level institutions, such as vocational schools, trade schools or career colleges, including their respective faculty, staff, and students.