An article on Tom's Hardware points to Cuba's plans to create their own Linux distribution called "Nova".
Quotes from the article:
"In an effort to rid every computer in the country of the American-designed Windows OS, the Cuban government has banned the software and created its own Linux-based operating system."
"Private software can have black holes and malicious codes that one doesn't know about. That doesn't happen with free software" - Cuba University's Information Sciences Director Hector Rodriguez
Read more here
This is not that unusual. China for example has long had various home-grown Linux distributions. Obviously there is both a security aspect as Rodriquez has noted above, but also a large political element to this.