Sexual activity is allowed, along with such things that are usually only found in a relationship (i.e. cuddling, going out on dates together, attending a social event together)
The second portion of "relationfriends" comes into play where it is more than acceptable for the two parties to engage in behavior that would be found in a plutonic (non sexual) friendship. It is proposed that this helps keep the balance in the friendship, so as to not get to attached through the use of seeing one another merely as friends occasionally.
Lastly, relationfriends should consider signing a notarized contract to secure the agreement and proper behavior of the ordeal. If one of the parties is found to be in breach of the contract (asking to be exclusive), the ordeal may be cancelled immediately by the other party for legal obligation if they so choose.
A common acronym to describe this binding agreement is: N.E.R.F. (Non-Exclusive RelationFriends)
Brian: "Yes. Yes. I agree. We should be relationfriends!"