This analogy is not new but very deceptive. First of all, there's nothing anti-Capitalistic about sharing something voluntarily. While in a Capitalistic country, goods are generally sold and have to be paid for, people can voluntarily dedicate their time and money for any cause they wish, possibly altruistic. Communism in fact forces the sharing of all good, including physical ones that take time and money to manufacture each unit of.
Secondly, because manufacturing and distributing a unit of software costs practically nothing, it is not necessary that it will be sold. While the development cost can be very large, a developer of the software will not be encumbered by it being used by a million people instead of a thousand.
Furthermore, by making a software open-source and keeping it so, it is possible to gain other economical and psychological advantages: you'll make sure it is maintained, gain feedback and admiration of others, and may be able to eventually receive input and contributions from the outside. Distributing a software as a commercial proprietary package does not automatically yield good advantages and it takes a lot of time and money to make it usable as well. Such a vendor is actually risking that his software will work at all, and not be out-competed by something better.
This analogy was rejected and treated in a semi-jokily manner by most people who did not oppose Capitalism as a whole. A true understanding of why open-source does not contradict the liberal ideals of Capitalism and individualism originated from Eric Raymond's "Homesteading the Noosphere" and "The Magic Cauldron", which are a very good read anyway you look at it.
The facts themselves do not give way to it either. The free software movement is almost entirely limited to liberal Capitalistic countries, which are free enough to allow unrestricted programming and distribution of software to prosper. Furthermore, I cannot name a single prominent figure who is Socialist or Communist, or otherwise entirely anti-Capitalistic (albeit some may hold certain views of this kind). Lastly, open source or some open source software was recently endorsed by many IT and non-IT businesses who greatly benefit from it, including some vendors of proprietary software.