Raven Software released some of its popular SDK's for their games (more specifically Soldier of Fortune 2 and Star Wars Jedi Knight: Jedi Outcast) on varioius sites throughout the internet as well as hosting a download on their own website prior to being bought out by Activision. It's a bit harder to find one now that is really validated, but you could try your luck around the internet. To be honest, any programmer with half a brain would know that the Internet is their best source of information and that is where you should've started looking, not Demobase.
http://soldieroffort...player_SDK;5824
There are more from some simple Google Searches, but I will start you off here. I'd assume the best people to speak to regarding developing a module for SoF2 would be Shifty (can be found on this site), Max (can be found here or wherever the remnants of RPM are), or anybody who develops a mod or similar game using the Quake 3 Arena engine. Here is a link to the source code of the Quake 3 Arena engine: https://github.com/i...Quake-III-Arena
Starting here will help you get your bearings. Here is a very good five part write-up on the architecture behind the Quake 3 Arena engine, which I'd highly advise knowing about if you really wanted to get into modding SoF2. http://fabiensanglar...uake3/index.php
Perhaps it's a lot more simple than this, but in all honesty, any programming isn't a cake walk either. Be passionate about it and spend hours and hours of your day working and learning and you'll more than likely learn how to make something people may or may not use.
By the way, there are people who still have the server side files for RPM and you could probably get your hands on that pretty easily. Reverse engineering is a great way to learn as well.
Edited by forgylicious, 30 December 2013 - 07:11 PM.