There's also a character cell frontend as well at:
Insight was indeed a separate project in recent years and it's development stalled at gdb 6.8. The website is:
As you say, the major disadvantage of Insight is that it's tightly bound to the gdb source instead of the more typical communication via a gdb protocol you have with the other GDB frontends. (IIRC, Insight also came with it's own copy of the gdb source).
That makes it unusable with later gdb versions and I switched to using ddd which works ok for my needs.