Well, the license is a main pro of course, because that makes it embeddable, and I'll certainly have a look. That appeals more to me than the GO stuff.
You could try to develop that idea further with a compile to memory option or so and a good demonstration (integrate in old dev pascal ide or so?).
If you are going for embeddability it might be good to rename some of the compiler units as their names are (literally) awfully COMMON
For bits and pieces like the bug that 440bx found you could try to harvest the FPC testsuite (and maybe pas2js has tests somewhere too for the fcl-passrc parser)