Downloaded the amplitude custom shop yesterday, which added amplitude 4 as a plug in to ableton. When first opening it, there was a message asking to authorize or skip, which I skipped. It has 2 or 3 Amps and cabs, a few stomp boxes and you can play with the mic placement a little. Is this a trial version that will expire in a few days, or are these portions of the software free?
If this is going to expire is there a way to purchase a standalone amp plug in through the custom shop to use with other cabs/ impulses, or is buying the amplitude 4 software necessary?

Also when purchasing software like amplitude 4 or something you need to authorize, is there a way to use it on my current pc and continue using on a different pc down the line? Does it matter if going from pc to Mac and possibly switching DAWs?
Talk to IK about all this - just email their tech support.

From what I saw in ver.3 you can just purchase a-la-carte, in other words just pay as you go, say you need Orange amp - you just pay for that. But first you have to buy tokens via their site and then use those token credits to whatever you want from the store.

You can use on more than one, I think 2 PCs at a time and it could be transferred. I think you can validate each 5 times, then you'll have to contact cust. support for a reset to activate more times. Is it Mac capable? I think at this moment it is.

You might also want to look at the free Guitar Rig PLayer 5 (free):
It is very usable light version of their big product.