A couple of points you may want to consider.
DOSBox is not really comparable to Amiga emulators because all of the required software components were already available under free licenses before it was created. Remember DOSBox is not just an x86/BIOS emulator but it also contains a re-implementation of DOS i.e. it doesn't contain any protected code from the IBM BIOS or QDOS/MSDOS/PCDOS/DRDOS. The x86 PC is an open architecture whereas it is not clear who owns the Amiga rights, even if there was a willingness to release Kickstart for free the cost to reach an agreement with all interested parties may be prohibitive.
WinUAE includes a free Kickstart replacement that is enough to play most games, only programs that actually use ROM functions require a genuine OS ROM, also keep in mind that although a lot of people on EAB still own Amiga hardware and therefore have legal access to the ROMs whether this gives any of us the right to use Kickstart ROMs for emulation purposes is not known for sure.
With the above in mind you may as well just "steal it" as the chance of the rights holders being able to pursue a legitimate claim against any of us is negligible.