Helix Code changed its name to Ximian, Inc. on January 10, 2001. The change was done, says the FAQ, " to provide trademark protection for our work. While our software is open source, and we encourage you to share and redistribute it, trademark protection means that you know where your software is coming from.".
As a clarification, I would like to say that the change does not mean that GNOME "went commercial" (Helix Code was already a commercial company) or that anything changes per se in the software they make: the change was necessary, I'd guess, to protect from namespace clashes with other entities.

Here is the letter that announced the change:

Dear Friends,

Today, Helix Code changed its name to Ximian, Inc. The name Ximian (which is pronounced ZIM-ee-un) differs from our old name in that we can actually trademark it and thereby ward off the legions of copycats who want to ride on our coattails. And it sounds cooler, too.

Everything else about us remains unchanged: we're the same company made up of the same great hackers writing the same free software. And yes, led by the same hyperkinetic American/Miguel de Icaza duo.