Hi Bruno,
We haven’t used Appboss and don’t have any data about its compatibility.

I do not see any issue for it to not work though. If the AppBoss is able to work with normal BuddyPress instance, they should work fine with multi network instances of BuddyPress.

There is a possibility that they might be doing some database updates directly(via plugin) and not using BuddyPress. In this case, there will be issue and there is nothing that we can do.

If you find any issue, Please contact AppBoss support and ask for a reason. If then need us to change something, we will gladly oblige.

Regards
Brajesh