Hi,
May I know on which distribution you are planning to deploy those apps? If it is ubuntu, than it can be done in the mentioned time frame.
I have few questions regarding this statement
"The ultimate goal is to create a completely new communications platform (based on the latest versions of the mentioned softwares), with voice calls, fax, Audio conferente, web video chat options, as the existing one we have and developed for our needs. "
This is something that requires more than installation of those modules, and you have not clearly mentioned about these tasks. So lets have a detailed conversation about it and start the project.
PS This is our new profile prior to this we were working on Peopleperhour and elance.
Thanks & Regards
Suman Dev