Was really looking forward to the j-core project and got into SH4 emulating the Dreamcast port of NetBSD which is currently available for the latest version which is 9.3 I believe.
There are also lots of interesting things going on with NAOMI emulation on the gaming side. All of it is very hackable and j-core would have made a great addition to that.
http://wiki.netbsd.org/ports/dreamcast/
GXemul is what I used at the time.
https://gavare.se/gxemul/gxemul-stable/doc/machine_dreamcast...
There are also lots of interesting things going on with NAOMI emulation on the gaming side. All of it is very hackable and j-core would have made a great addition to that.