Here is what worked for me.

kraem> ~/bin/zcat samba-3.0.31.tar.gz | tar -xvf - ; cd ./samba-3.0.31/source/
kraem> CC=cc CFLAGS=-O2 ./configure
kraem> cd ./source/utils/
kraem> diff net_rpc_samsync.c net_rpc_samsync.c.orig

1742c1742
<       char *add_name = NULL, *modd_name = NULL;
---
>       char *add_name = NULL, *mod_name = NULL;
1782,1783c1782,1783
<       modd_name = talloc_strdup(mem_ctx, mod_template);
<       if (!add_name || !modd_name) {
---
>       mod_name = talloc_strdup(mem_ctx, mod_template);
>       if (!add_name || !mod_name) {
1794,1795c1794,1795
<       if (!(mod_file = fdopen(smb_mkstemp(modd_name),"w"))) {
<               DEBUG(1, ("Could not open %s\n", modd_name));
---
>       if (!(mod_file = fdopen(smb_mkstemp(mod_name),"w"))) {
>               DEBUG(1, ("Could not open %s\n", mod_name));
2020,2021c2020,2021
<       if ((modd_name != NULL) &&
<           strcmp(modd_name, mod_template) && (unlink(modd_name))) {
---
>       if ((mod_name != NULL) &&
>           strcmp(mod_name, mod_template) && (unlink(mod_name))) {
2023c2023
<                        modd_name, strerror(errno)));
---
>                        mod_name, strerror(errno)));


kraem> gmake ; gmake install
kraem> /usr/local/samba/sbin/smbd --version

Version 3.0.31

kraem> AIX OS Level Information

Fileset           Level    Description
------------------------------------------------------------------------------
bos.rte           6.1.1.0  Base Operating System Runtime
bos.mp64          6.1.1.1  Base Operating System 64-bit Multiprocessor Runtime
xlC.adt.include   9.0.0.0  C Set ++ Application Development Toolkit
xlC.aix61.rte     9.0.0.8  XL C/C++ Runtime for AIX 6.1
xlC.cpp           9.0.0.0  C for AIX Preprocessor
xlC.msg.en_US.cpp 9.0.0.0  C for AIX Preprocessor Messages--U.S. English
xlC.msg.en_US.rte 9.0.0.8  XL C/C++ Runtime Messages--U.S. English
xlC.rte           9.0.0.8  XL C/C++ Runtime
------------------------------------------------------------------------------

-frank-