I have this phone, but have not yet tried this switch to GSM. But, I know that several former R+ members also had this phone, and one might know if this method works for US GSM carriers, or some might just want to try it. Funny: at the end of the article the author mentions that one should keep the Sprint sim because it can be used with Ring+.
I had this phone, too-- as did many of the RingPlus members. I think the easy GSM unlock only works for international unlock. A number of folks used it with the FreedomPop Global SIM after this switch-- but FreedomPop is discontinuing the free plans on the Global SIMs, so less of an advantage there.