I did email the BPF kernel mailing list, they directed me to two user-land (user-space?) implementations of BPF but didn't say much about what "user-space BPF"

I did email the BPF kernel mailing list, they directed me to two user-land (user-space?) implementations of BPF but didn't say much about what "user-space BPF" meant. Didn't want to clutter up the mailing list with noise so I didn't reply: https://lore.kernel.org/bpf/Y3BQGgcCMaSptEFJ@google.com/T/#t https://lore.kernel.org/bpf/Y3BQGgcCMaSptEFJ@google.com/T/#t