Rubbish, he is perfectly entitled to use a kickstart rom image AND full set of workbench disk ADFs as supplied with his A2000 AS HE ALREADY OWNS THEM.
This is not true. What he bought with his Amiga is a single-place license. This means he may use it with one machine only. Strictly speaking he has to remove the ROM from the A2000 and erase the harddrive if he wants to use the ROM and ADF images in WinUAE.
Let's face it, everybody uses his/her self-made or downloaded ROM and ADF files on every PC he/she owns without taking care about licenses and such. Yes.
But it's simply not true to say that it's legal. It's not.