Sailfish OS!

Replicant is a distribution of Android that is 100% Free Software.

Windows 10 Mobile is a mobile operating system developed by Microsoft. Some features include : Live Tiles, Kid's Corner, Photos + SkyDrive, Rooms. It also allows you to Take your Word docs, Excel spreadsheets, PowerPoint presentations and OneNote notebooks on the road, and automatically upload every photo and video you take on your phone to SkyDrive for safekeeping (with a choice of full or lower resolution).

Tizen is an open source mobile and device operating system based on Linux developed by Samsung and Intel.

Plasma Mobile turns your phone into a fully open hacking device, just like a PC. You can join us to start building new mobile experiences now.

OnePlus launches their own Lollipop-based ROM. Available now for download: http://downloads.oneplus.net/

B2G is a community maintained open source operating system for smartphones, tablets, smart TVs and other connected devices. The project was started in 2011 and is based on the Linux kernel and Gecko rendering engine. The entire user interface is built using web technologies (HTML, CSS and JavaScript) and can be used to launch and use web applications. Since Mozilla discontinued their commercial Firefox OS smartphone program the smartphone part of the project is entirely maintained by Mozilla's volunteer community, and branded as B2G OS. »

Astian OS, is an operating system based on Firefox OS, developed by the Astian Foundation. Astian OS was born in 2016 with the objective and mission to innovate in the world of mobile operating systems and to continue the work of having a mobile operating system developed with HTML 5, CSS, and JS. Astian OS is scalable open and is a platform that allows to interact with the devices from the web with great orientation to IoT.

H5OS is a mobile OS based on Firefox OS developed by Acadine Technologies.