The current section pertaining to mongodb.release.directory and mongodb.release.autoDownload is pretty good but I would like to see it expanded to include a note that in addition to security concerns it may also be that the internet is just not available.

So in this case add something like:

If you cannot or will not enable the OnPrem Service to download the community versions of the mongodb packages directly from the internet, then you must download them your self and place them in the appropriate locations with the correct structure.

For example, if you are backing up a 2.4.10 based replica set using the default mongodb.release.directory (/opt/mongodb/mms-backup-daemon/mongodb-releases/) then you must do the following :

$ wget https://fastdl.mongodb.org/linux/mongodb-linux-x86_64-2.4.10.tgz
$ curl https://fastdl.mongodb.org/linux/mongodb-linux-x86_64-2.4.10.tgz.md5  
aa88938437f27b8e11f82e1cfb63b4e8
$ tar -C /opt/mongodb/mms-backup-daemon/mongodb-releases/ -zxvf mongodb-linux-x86_64-2.4.10.tgz 

If you are backing up an enterprise version then the same community version of the mongodb package will suffice. For example 2.6.1 enterprise will require :

$ wget https://fastdl.mongodb.org/linux/mongodb-linux-x86_64-2.6.1.tgz
$ curl https://fastdl.mongodb.org/linux/mongodb-linux-x86_64-2.6.1.tgz.md5 
d3e5505d95c67ba52206960995655ec7
$ tar -C /opt/mongodb/mms-backup-daemon/mongodb-releases/ -zxvf mongodb-linux-x86_64-2.6.1.tgz 

Note: if you are backing up multiple versions then you must download and install the tarballs for each version used (currently the downloads are available for http://www.mongodb.org/downloads)
If you feel you must use the enterprise version as the Head node then you will have to perform a further step to ensure that the directory names match. For example, assuming you have downloaded the 2.6.1 enterprise version:

$ tar -C /opt/mongodb/mms-backup-daemon/mongodb-releases/ -zxvf mongodb-linux-x86_64-enterprise-rhel57-2.6.1.tgz 
$ mv /opt/mongodb/mms-backup-daemon/mongodb-releases/mongodb-linux-x86_64-enterprise-rhel57-2.6.1 /opt/mongodb/mms-backup-daemon/mongodb-releases/mongodb-linux-x86_64-2.6.1

Note : in this case you will also need to ensure that the additional libraries required by the enterprise version are correctly installed and available.