Which is the difference between IMA (B777) and Open IMA (A380)? The integrated modular avionics concept (IMA) was developed by Boeing for its B777. Open IMA is an improved version developed by Airbus starting from A380. Which are the differences? For example, I got that the network is optical fiber for IMA and Ethernet/Avionics Full-Duplex Switched Ethernet (AFDX) for Open Ima: why?

I know that the question may be too broad and not very easy, so I would welcome even some links to deepen the argument. 

Moreover I would like to understand: where is it used IMA nowadays? Only in B777, or even in B787 and new generation B747 and so on? Idem regarding Open IMA: only A380 or even in the A329 Neo? 

If Boeing and Airbus have these new systems, what do you have in all other companies? Embraer, Eurocopter, Tupolev etc.
The primary difference is that the B777 is the AIMS (airplane information management system).  It is a Honeywell developed system where all the software on the systems is controlled by Honeywell (closed system).  The biggest downside to the closed system is maintenance and support.

The A380 system is a semi-open IMA system. It has a single supplier hardware cabinet with processor slices and an common operating system.  Different suppliers can develop their applications to run on the platform.   

Most newer aircraft designs use the IMA architecture as it reduces the number of LRUs and saves weight.  Boeing and Airbus are going to more open systems.  B787 and B777X are open as is the A350, mainly for competition reasons.  Smaller aircraft (Bombardier, Embraer) are typically closed as they tend to have single source avionics (Rockwell Collins, Honeywell).