How can I run command line software with Rosetta 1?
Provided you're on a system where Rosetta v1 is available (up to and including Mac OS X 10.6), you can direct the system to execute the ppc segment of a universal binary using the arch command.
/usr/bin/arch -arch ppc /path/to/some/executable

I've found it useful to keep a virtual machine in Parallels Desktop running OS X Server 10.6 with Xcode and other developer tools installed for this scenario, of compiling older software for obsolete PowerPC Mac systems.