The xterm and nxterm programs under at least RH 5.1 and 5.2 use the SAME termcap entries but exhibit DIFFERENT characteristics. To demonstrate, open an xterm and an nxterm, and in each type 'cat >/dev/null' and then press F1 through F8 then ctrl-c and do a 'printenv TERM'. The net result is that any text-based program which uses function keys will fail depending upon which type of xterm the end user is using. An obvious solution is to have the nxterm use the 'nxterm' terminal type, except this won't work properly because there is no /etc/termcap entry for nxterm (there IS a terminfo entry). So the problems are: #1: xterm and nxterm behave differently but claim to be the same #2: the terminfo database is inconsistent with the termcap database (Note: Modern xterm implementations such as Solaris seem to be using the nxterm function key method. For maximum interoperability with remote-logins it is best to at least try to use the same conventions as everyone else)
nxterm has been dropped from the distribution in 5.9beta and later. Modern xterms do everything that nxterm did and more.