I think the deal is that the salute command existed in RTCW, but didn’t do anything. It is not uncommon to have features which are not fully implmented. shrub (in rtcw) just made it do something. This was helpful for shrub mod, because he could add a ‘new’ command while still having a server only mod.
I haven’t played on shrubs et server, but based on other peoples reports, it does sound like it has been modified in some way. While it is possible to make mods without the source, it is quite difficult.
If it is true that he has the source, I really hope splash (or id or activision) considers giving out to other people. IMHO, with some fairly minor changes ET would be much more attractive as a competition game. I would be happy to sign an NDA or additional license agreement to get access to the source.