I'm sure it can, Joomla! RULES!! but I guess ISPConfig add all kinds of wierd resrtictions to safemode.
Because the error says "open_basedir restriction in effect" now I'm very new to Linux and the PHP/HTML enviroment, but I think Joomla was trying to place the files to be insatlled in their correct directories, and it started at the "/var" directory searching up the directory tree, and because "/var" is not allowed to be read by any website with safemode, it threw me an error.
thats my logic I suppose, all PHP professionals PLEASE COMMENT, I gotta learn someday, lol.