Meltemi was a Linux-based operating system that was intended to be Nokia’s successor to the S40 feature phone platform. Used in conjunction with the Qt development toolkit, Meltemi was going to be the cornerstone of Nokia’s strategy for connecting the “next billion” smartphone users.

via Nokia’s Linux-based Meltemi platform melts amid layoffs; Qt still afloat | Ars Technica.

It’s worth noting that the Qt toolkit is widely supported by other parties. Nokia’s decision to relicense Qt under the permissive LGPL has made it possible for other smartphone vendors to adopt it as part of their platform. HP was using Qt in webOS and RIM is currently using it as the basis for the development toolkit in its next-generation Blackberry operating system.