nuBuilder Forte is the name of version 4 of nuBuilder. It is supported by nuSoftware and available on GitHub.
History of nuBuilder
nuBuilder version 1 was first released in early 2009 to a limited number of commercial users. In early 2012 nuBuilder version 2 was released and made open source by nuSoftware. nuBuilder version 3 (also known as nuBuilderPro) was released in January 2014 and is available on GitHub.