This looks like a Green Singing-Finch aka Yellow-fronted Canary (Crithagra mozambica) (used to be Serinus mozambicus). It's an African species that is fairly common in the pet trade, bred frequently in captivity, and has a few feral populations in Hawaii, Mauritius, and Reunion.
@Jena You're very welcome! And I should have added that I've kept this species and they are wonderful birds. I have a male that I purchased from a pet store in 2009, so he's at least 15 years old and still going strong. Surprisingly long-lived for such small birds.
