I see earlier this month set_escdelay extension has been added to libcurses. Now audio/moc finds it and configures it (in interface_elements.c), but dumps core on invocation:
➜ moc-2.5.0 ./mocp .
Running the server...
Trying OSS...
[1] 1918 segmentation fault (core dumped) ./mocp .
➜ moc-2.5.0 ESCDELAY=25 ./mocp .
➜ moc-2.5.0 gdb ./mocp ./mocp.core
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Reading symbols from ./mocp...done.
[New process 1]
Core was generated by `mocp'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0 0x00007101d1a157b3 in set_escdelay () from /usr/lib/libcurses.so.7
(gdb) bt
#0 0x00007101d1a157b3 in set_escdelay () from /usr/lib/libcurses.so.7
#1 0x0000000000420a71 in windows_init () at interface_elements.c:3627
#2 0x000000000041850b in init_interface (sock=sock@entry=4, logging=0, args=args@entry=0x7101d21012a0)
at interface.c:3504
#3 0x000000000043b58c in start_moc (args=0x7101d21012a0, params=0x7f7fff188fc0) at main.c:217
#4 main (argc=<optimized out>, argv=<optimized out>) at main.c:855
(runs OK if started with 'ESCDELAY=25 .mocp .' - in this case set_escdelay is not invoked).