Complex sentence: Shuttleworth founded Thawte Consulting in 1995, which specialised in digital certificates and Internet security, and then sold it to VeriSign in December 1999, earning R 3.5 billion (about US $575 million at the time).
Split into simpler sentences: Shuttleworth founded Thawte Consulting in 1995, which specialised in digital certificates and Internet security. In December of 1999, Thawte was acquired by VeriSign, earning Shuttleworth R 3.5 billion (about US $575 million at the time).