You never heard of dll hell? Isn't that a windows term? At any rate, the
registry isn't some advantage of windows, but a clunky mess. Linux
distros have always had shared libraries, and multiple coexisting
versioned libraries. There is no problem running multiple versions of
programs on linux, each with its own library dependencies, since in
linux, every single process has it's own dedicated environment, which is
isolated from the environments of all other processes.

Whatever the problem with skype, it's not any inability of linux to
handle different dependencies for different binaries. Either the coders
are not knowledgeable enough of linux to write good apps, or the
management doesn't want to spend any resources on a linux port, or both,
but the end result is that we get a half baked, half-hearted version of
skype on linux.