Is Cisco's EIGRP proprietary or not?

Hi folks,

short question, is EIGRP propritary or not?

FRRouting has implemented EIGRP: http://docs.frrouting.org/en/latest/eigrpd.html

RFC7868 descripes EIGRP: https://tools.ietf.org/html/rfc7868

Where is the difference between FFRouting EIGRP and EIGRP implemented in Ciscos hard-/software.

Have anyone experience with that?

BG