Using dot or "source" while calling another script - what is the difference?
The only difference is in portability.
. is the POSIX-standard command for executing commands from a file; source is a more-readable synonym provided by Bash and some other shells. Bash itself, however, makes no distinction between the two.
There is no difference.
From the manual:
sourcesource filenameA synonym for . (see Bourne Shell Builtins).