So apparently, as long as you aren't using a mixture of unofficial and official IOS copies to get extra support from Cisco, it doesn't seem like you're breaking the spirit of their licensing agreements to use an ios copy from, say, a cheap router on ebay (copy flash tftp etc).A customer buys mostly unauthorized used gear, running un-paid for IOS images, plus a few legit routers/IOS's with a maintenance contract. When the unauthorized gear breaks, the maintenance contract on the small number of legit devices is used used to get TAC help, IOS upgrades, and even in some cases, replacement hardware.
I'm assuming you mean an IOS image for GNS3? Then yes, official way to own a copy is to buy it from cisco. Unfortunately, that's expensive. Really expensive. And a large chunk of that expense is due to service agreements that come with it. Regarding why they haven't made copies to study with yet:
So apparently, as long as you aren't using a mixture of unofficial and official IOS copies to get extra support from Cisco, it doesn't seem like you're breaking the spirit of their licensing agreements to use an ios copy from, say, a cheap router on ebay (copy flash tftp etc).
Unfortunately, you can't just buy an IOS image. you have to buy a support package for a product that gives you access to updated images among other things. And that's much, much more expensive than ebay routers. I haven't found an exact price tag, but I've seen $1,000 thrown around as an approximation.How much is the image? I can't really afford second hand gear at the moment.