Leo
terminals need a "server" to work.. if you can make boot them from ethernet, you can use
LTSP to boot ubuntu or another linux distro and then you can use them to connect to internet..
I've done some testing with 2 virtual machines:
- a SME one for users, dhcp service, file/mail/ssh services
- a ubuntu one (9.04) installed with "create a terminal server" option.. joined to SME
I was able to boot from lan with a thin client, auth myself on SME, browse internet, read email (from SME, of course) with firefox/thunderbird
it's not trivial, but it's not impossible
I repeat, you have no other choices