I think he licensed the portable installation incorrectly.
I've never done this, but I think the way it works is this:
1. You have to have installed and registered a copy of MC (non-portable, regular installation) on a computer.
2. You then use THAT computer to install the Portable copy onto your USB drive (or whatever). That's right, you "install" MC on a computer that already has a copy installed and licensed, you just pick "portable" this time and install it somewhere else.
3. That copy will retain the licensing.
4. If you want to update the portable install to a new build, you go back to the computer in step #1 and update it using that computer.
If you don't do step 1 first, then you'll end up with trial mode portable installations.
As far as your other question, you are allowed to install MC "normally" on the computers you own and use personally without buying additional licenses. So, for example, a home desktop machine and a HTPC or laptop would be fine. That's the purpose of the ten restores per year (and to allow for additional nuke/paves on temperamental windows machines).
The way I divide it is that for my machines I use at the office, I've bought a second license of MC for those machines, because they are "owned" by my company, not me. For my machines that I own personally and use at home, I use my "personal" license for MC.