> ===> build-message [xisp-2.6p1] ===> Building for xisp-2.6p1
> gcc -Wall -O -DBINPATH=\"/usr/sbin\" -DLIBPATH=\"/usr/pkg/libexec\" -DOPTPATH=\"
> xisp.c:21: forms.h: No such file or directory
> *** Error code 1

Hi, this is because the patch-aa did the bad thing.
You could do following steps:

1. replace the first section of patch-aa with this:
@@ -8,11 +8,11 @@
 #  Compilation/installation vars (global for all following sections) |
 #=====================================================================
 #
-PREFIX     = /usr/local
-X11PREFIX  = /usr/X11R6
-INCX11     = $(X11PREFIX)/include
-LIBX11     = $(X11PREFIX)/lib
-INCFORMS   = $(X11PREFIX)/include
+#PREFIX     = /usr/local
+#X11PREFIX  = /usr/X11R6
+INCX11     = $(X11BASE)/include
+LIBX11     = $(X11BASE)/lib
+INCFORMS   = $(X11PREFIX)/include/X11
 LIBFORMS   = $(X11PREFIX)/lib
 MODEM_DEV  = modem
 MODEM_PATH = /dev/$(MODEM_DEV)

2. type 'make makepatchsum'

3. add this line into Makefile:
--- /usr/pkgsrc/comms/xisp/Makefile     Sun Mar 17 17:26:59 2002
+++ Makefile
@@ -16,6 +16,8 @@
 USE_X11BASE=           YES
 USE_XPM=               YES
 
+MAKE_FLAGS+=           X11PREFIX=${X11PREFIX}
+
 post-install:
        ${INSTALL_DATA_DIR} ${PREFIX}/share/doc/xisp
        ${INSTALL_DATA} ${WRKSRC}/README ${PREFIX}/share/doc/xisp/

Then you could build it normally.
Good Luck!

-rxg