That 438.010 MHz is an input frequency for amateur TV repeaters (As per the ARRL band plan). JOTA is a Boy Scout event.. It's not much of a calling channel if you can only use it as a calling frequency during the Boy Scout's Jamboree On The Air.
There are agreed upon simplex frequencies for D-Star on HF.
D-STAR HF Net - D-STAR Info
But, I don't believe there are any nationally recognized (ie ARRL) general calling frequencies for VHF/UHF digital voice emissions. Gets kind of muddy... For instance, what are the simplex calling frequencies for DMR, P25, Fusion etc?? I think calling frequencies for these modes would be something agreed upon by local users.