First time I tried to run I-TASSER 5.0 with "-runstyle gnuparallel", I got the "time: command not found" error as soon as it got to the threading stage.
Turns out that on Arch, the time command is not installed by default; by default only the bash built-in time keyword is available. Not sure if other distributions do not install the time command by default. Anyway, simply installed it and everything ran fine.
It may be a good idea to specify that requirement somewhere. Or to do a check within the scripts like it is done for the parallel installation (check for "which time" similar to the existing check for "which parallel"). Although for most, I guess the "time: command not found" is pretty self-explanatory...