Well according to bitnodes in terms of software you do have this guy https://bitnodes.io/nodes/?q=Satoshi:0.8.0

As for longest running node / service. Tough to say.

If you refer to people or group who run Bitcoin full node until now, i doubt it’s ACINQ since they founded in 2014. I expect it’s either,
1. Certain early adopter/developer who still use Bitcoin until today.
2. One of cryptocurrency company which run until today. I recall blockchain.com and BitPay founded in 2011.