As far as I can see, it seems to be self contained :
https://docs.netdata.cloud/installer/#pfsense
extract :
Note first three packages are downloaded from the pfSense repository for maintaining compatibility with pfSense, Netdata is downloaded from the FreeBSD repository.
pkg install pkgconf
pkg install bash
pkg install e2fsprogs-libuuid
pkg add http://pkg.freebsd.org/FreeBSD:11:amd64/latest/All/netdata-1.11.0.txz
the netdata package does not seem to add extra dependencies unless I'm looking wrong
but something like netdata (also like ntopng) is designed to run 24/7
I'm running it on a test pfsense in an isolated network, for now the test setup seems to run