We cannot keep developing things for ppl who have outdated hardware by several generations. Sorry, but that's the simple truth. People with hardware current to like 2003 simply are no longer a target audience. Yes there's a lot of them, but they can hardly be considered serious gamers. It sucks, I know HLEV. For years I had an outdated computer with a 933 mhtz Pentium 3, and a 64 MB PCI Voodoo 5 5500 in it. I couldn't even run HL2 and I had the comp until 2007. I had to buy a new comp eventually. People are going to need to buy new stuff, and not just expect everyone to develop low end graphics apps so they can run them. It's not a realistic expectation.
And, this is a mod, even how graphically nice it is, I expect computers from 2005 should be able to run it pretty nice..though I haven't actually tested the build, I can't imagine they've ramped up the requirements to 2009 / 2010 levels.