Re: Cost is the smaller concern
"someone else's hacked and undocumented spaghetti code?"
Citation needed as to your assumptions.
However let's look at what might be involved. As research is so difficult I've taken the liberty of cutting and pasting this from their website:
Our customisations are as follows:
-A look and feel similar to a well known desktop…
- NHSmail2 compatability
--Email, calendar, address book
--Messager, with file sharing!
- N3 VPN compatability
--RSA token supported
-Remove games packages (sorry folks, no Minesweaper!)
-Added Remmina, a Remote Desktop client for VDI (or whatever it’s called these days)
Yup, maintaining that is going to be far too much of a challenge.