You don't need to set jb_cstrike15. It should work automatically with CS1.5. Also, jb_* cvars don't belong in bot.cfg, they go in joebot.cfg. I tried the following with CS1.5 which I think starts a lan server:

hlds.exe -console -game cstrike +exec server.cfg +maxplayers 10 +map de_aztec +sv_lan 1 -nomaster

I tried it about 3 times without any crashes. I'm assuming you unzipped the archive into your half-life directory. You should have a new liblist.gam in Half-Life\cstrike directory and all the .dll and config files in Half-Life\cstrike\joebot directory.