Version of XCode
From OpenFOAMWiki
Fragment of a discussion from Talk:Installation/Mac OS/OpenFOAM-1.6-ext
I guess MacPorts requires the command line tools because although they deliver binary packages nowadays technically it is a "source only"-distro and even if it would use its own compiler it would need some compiler to bootstrap the compilation of that. Which happens to be the XCode-compiler. Plus there may be other utilities that are MacOS-X specific and for which no OpenSource-alternative exists (the linker?)
About rpm: without the error message it is hard