If you have done it in Linux, odds are it should compile with GCC on OS/2.
You have to use ANPM to install the build environment. Unluckily there is no meta-package so you have to install all of the build environment piece by piece using ANPM (or YUM on the cmd line).
To start, install GCC and its dependencies. Libc-devel, libcx-devel, various *nix utilities such as flex, bison etc, kbuild-make for make. Likely the autotools such as autoconf, libtool and such.
Building on OS/2 isn't too different then building on Linux, assuming the source is portable.
Gotchas include, having to rebuild the autotools stuff so configure etc knows about OS/2. Usually with
sh x:/usr/bin/autreconf -fis
Replacing x: with your @UNIXROOT, likely your boot volume.
Other Gotchas is needing LDFLAGS=-Zomf to get the right object format and use the system linker and allow debugging with -g (don't forget to install gcc-wlink) often linking with -lcx as libcx is some libc extensions and various others I'm sure I'm forgetting.
Best is once you get the above installed, ask here for advice if you run into problems. I have no idea how experienced you are at porting or how well Lore bbs supports OS/2 out of the box. OS/2 is DOSish, needs files opened in binary mode and things like that.
Good luck and keep us posted.