You are correct. Professional edition has been removed. We have simplified it so that there are now only two editions: Free/Standard, and Commercial/Enterprise.
LiteSpeed licenses by CPU-cores, not CPU sockets so a Mac Duo-Core would be 2 CPU cores and requires the 2 CPU-Core license for maximum performance. Note that you can use the 1 CPU-Core license on a 2/4 CPU-Core machine, it just won't scale to the number of cpus.