Have you had the same sentence being said to you before? It doesn't matter if it comes from his or her mouth, it's just the same for both sex. He or she still wants to be with you but at the same time wants to be free from any commitments of a normal intimate relationship. We called this an "Open Relationship", which specifies a relationship between two people, and these two people or either one of them is free to have other partners.
Some people who are involved in open relationships may have a mutual agreement on permission of sex outside of the primary relationship, however there should be no feel of "love" involved.
Open relationship is not anymore a taboo in our world today. It is seen, however subjectively according to individuals as a test of the strength of a bond in a relationship.Would you (or your heart) accept it as that? That is a highly subjective question that maybe you yourself are the only who can answer it.
Occasional intimate relationship with another party besides your partner is something casual for an open relationship and may have little impact on the level of intimacy of the primary relationship but frequent activity, may find even the most tolerant partner to feel even a little nudge of jealousy, unhappy and displaced roaming over. It is human nature, and it is hard to fight the nature of how things are and should be.
This is all the same; eminently depend on a string of related factors, regardless if the relationship you create is "open" or "close". This is the part where all your beliefs, thoughts and opinion of things and how things are and should be play a bigger part. Whether it is on the issue of morality, relationship and sexual ethics, personal preferences and mostly, your tolerance for obscurity and uncertainty, you are the one who decide things through. You should give a thought to being honest and fair to yourself and to your partner.
All the best! :)