A download of the version first used to make the hpb_bot and realbot wip for linux is allready here:
[removed, updated see below]
/edit
i made new releases, there are now two downloads:
one archive containing only the hlsdk-2.3:
BU-hl-sdk-2.3.tar.bz2
and a second archive containing the hlsdk-2.3, metamod sources and hpb_bot sources:
BU-hl-bot-build-example.tar.bz2
The fist pack is the hlsdk used internal by the bots united server, it should work for windows and linux, but i suggest to link only against the multiplayer tree, for me the singleplayer tree does not look fully updated.
The second pack is suitable to compile metamod and hpb_bot on it's own, a perfect startpoint to develop bots in linux and probably also for windows. The hpb_bot code is from march 3., i assume that's the lates version provided by Pierre-Marie.
Small readmes are included in both archives, if any questions arise feel fee to start a FAQ in the
wiki 
(section server wiki or developer wiki)
edit/
cheers memed