I was looking at this in the retrospec that if i buy the apps i should be able to use them on the devices i own. So therfore i would want to be able to put say it on two ipod touches, if i legally own two of them.
Well, that sort of logic has a long, long history from "regular" computer applications. Typically speaking you don't buy software, you purchase a license to use that software in a specific way. Some licenses are "per user" so you would be able to use that software on any touch you own, or even use, as long as no one else uses the software. Some are "per machine" licenses, so anyone who uses the machine can use the software, but only on THAT hardware. Some are even "per CPU", so you need a license for each processor in the machine that is running the software.
In the case of the touch, I'm guessing it's a "per machine" license.