Yes, all the CD-based games are region free.
One small correction... there are a few (under 5?) Japanese SCDs that will
not play on the US system. This appears to be due to a difference in the
Super System card version that was used between the US and Japan, and
not due to any region lock out, though (the Japanese card is 3.00 and the
US is 3.01).
Bonanza Brothers, A. III, Alshark and the Far East of Eden Demo on
the SCD RPG sampler are the 4 that come to mind that will not play.
There may be a few others that are escaping my memories at this point though too.
-bt