Hi Jason,
Seamonkey requies Xlibs.tcz to start. It's hard to encounter this problem because in most of the cases, a user load Xlibs.tcz prior to lauching Seamonkey. However, if a user run ssh -X to Core Linux, it might be more natually for the user to lauch Seamonkey without installing Xlibs and under that circumstance, Seamonkey won't start.