From your statement "I am a Frontend developer,I code offline web apps.." I would guess that
are not (yet!) an expert in operating systems and embedded controllers.
As a "Frontend developer" you deal directly with the properties and methods of a browser environment
and do not need to know very much about the huge amount of different software components and layers
that are needed in order to run a browser.
To find the best solution for your needs, you first need to define the following 3 basic elements of your idea
(in the following order..) :
1/ The browser requirements
- As a "Frontend developer" this is the most important layer.
You need to clearly define the requirements of "...something like Firefox OS but obviously in a very minimal way..".
You gotta have a clear idea of the set of browser functions needed for "...the users to develop web apps for the platform..
start moaning & groaning (!)
2/ The operating system requirements
Look for the smallest, lightest version of Linux that supports a full-featured firefox browser but stripped of all the stuff you don't need.
YOu can do this yourself but you gotta know all sorts of Linuy geeky stuff & this will take you some time if you are new to Linux config stuff.
I suggest you look for the smallest, lightest preconfgured Linux that supports your chosen browser:
G$$gle for "smallest possible embedded linux" & dig around
provides a good initial overview http://elinux.org/Best_of_Embedded_Linux
summarizes the currently available distros
And then ask the forums what can still be removed & how to do this..
3/ The hardware requirements
This will depend on the Linux distro that you choose.
I suggest you first look for the cheapest & most popular HW that will run the Linux distro you have chosen.
Even if newer & more powerful units seem attractive, using a popular system (e.g. Raspberry PI) will provide
you with a huge base of support/experience/tools from many experts, which will help you greatly if
you run into problems.. Sometimes it is better to choose the most popular system than the most appropriate (on paper) system
OK.. Nuff said..
IMHO, once you have defined the browser environment that you really want,
the decisions on the Operating System and HW should be relatively easy and obvious...