Per https://groups.google.com/g/comp.sys.amstrad.8bit/c/HtpBU2Bzv_U/m/HhNDSU3MksAJ :

"Amstrad are happy for emulator writers to include images of our copyrighted
code as long as the (c)opyright messages are not altered and we appreciate
it if the program/manual includes a note to the effect that "Amstrad have
kindly given their permission for the redistribution of their copyrighted
material but retain that copyright"."

With that in mind, Amstrad have kindly given their permission for the redistribution of their copyrighted material but retain that copyright. Material expected here, copyright Amstrad:

plus3.rom	— the +2a/+3 ROM file, 64kb in size.