This was my understanding of the license as well. I read through the block and it very clearly suggested only selling the database as a service was not okay. Using the database as a data store should be fine.

If MongoDB really is sending salespeople to make claims against companies who they convinced to use their OSS database as a data-store, than they are indeed abusing their license and no one should use their database or support their company.

From what I read of the license, that shouldn't be the case though.