Even *if* there *might* have been some code snippets in the first releases of MorphOS that *might* have been *lent* from OS3.x (which i personally don't believe!) - we are at MorphOS version 2.5 now! So AFAIK there's nothing illegal about it - it is it's own operating system, API compatible to AmigaOS 3.x. I would compare it to UNIX/LINUX - both show similar or identical APIs (POSIX) - even if SCO tried to sue LINUX supporting companies for years without success...
