Only if the library install doesn't open up a dialog, such as picking a mirror repository, and you need to run ggplot without a UI. it needs to plot to a file otherwise both instances run the risk of competing / corrupting the JMP application's main window loop. It's a limitation of Python running from within JMP's process space instead of as a standalone executable.
It's probably better to do R package installs from the R environment outside of JMP. There is no special JMP specific space for R package installations, it just uses the R environment's R packages.