PSK63F is available on the soon to be released versopm 3.13 of fldigi. You can download the beta test version for various OS here:
http://www.w1hkj.com/alpha/fldigi-flarq/ This version also supports new modes, PSK-125R, PSK-250R and PSK-500R; the R indicating Robust. These modes are similar to PSK63F, but also include an interleaver. You can learn more about these modes here: http://www.w1hkj.com/Fldigi-Help-3.13 Source code for fldigi is always available for alpha and release versions. 73, Dave, W1HKJ fldigi development team
