But who cares about Google Earth? Nobody has it installed anymore (that I know of). I'll invent a name for it; hypeware.
We do have an active and forward moving project for replacing Skype with entirely free (as in freedom) software that offers standards compliant mesh networks as part of the FSF skype initiative. This effort includes active releases of our sip protocol mediation server, GNU SIP Witch, which is already a formal package in the GNU Project, as well as development of a mesh capable free software client as part of GNU Free Call. I would not describe what we do as "open source", as we are a free software project, but we do fully welcome all participation. Information about our architecture, plans, and activities can be found at http://www.gnutelephony.org. We are also developing SIP connectivity as an addon to friendica, which is secure and federated distributed social networking that already works.
In regard to reverse engineering Skype, it is not a process we are interested in, as we want to make sure the foundation is designed from the beginning to assure privacy and support anonymity, as well as federated operation, rather than imposing a provider as a mediation between all communications or for finding users. We don't wish to replace Skype so much as we wish to make the need for "a" Skype, as something that needs to be hosted or otherwise controlled by a single provider, to disappear. We are interested also in entirely self-organizing calling networks, such as for emergency services.
However, I will note that while we (within GNU Telephony) are not ourselves interested in it, reverse engineering is by itself an entirely legal and protected activity when done correctly.
It reminded me very much of microkernel developers.
I think Marble is the closest thing that exists to fulfilling the goals of an open Google Earth replacement. Though again, I admit it has a few rough edges. I don't really like Google software anyway. They tend to make nonfree software that needs WINE libraries or open core software like Chromium that is a bad port of the Windows version and opens your system up to attack from what claims to be a security feature. I think Google just has no idea how to write good software and the abundance of Windows programmers that they hire probably doesn't help.