The pricing is pretty much 'per running instance' of the toolset. If you have 1 seat, you can run one 'console' and one agent. The agent can be on a different machine... you connect to it, usually with TCP/IP. So you can install onto as many machines as you like, but only use as many at a time as you have seats. This requires a 'license server' which segue supplies that keeps track of when to let new instances start up.
Regular SilkTest supports xp, 2k, nt, 98, & me, I think. International only supports xp, 2k, nt.
I know nothing about as400.
Chris R Mead
The opinions expressed herein are my own personal opinions and do not represent my employer's view in any way.