I don't know about VivaDesigner (never looked for an alternative anyway), but I hope people know about Scribus. LaTeX is a bit too manual for someone coming from InDesign, so it's not a real alternative in that sense. My point was, that people have projects and files created and maintained with the Adobe software. Unless the programs are 100% compatible with the alternative, it's hard for many to make the switch. Plus they would need to learn a new "complex" tool, and know exactly which one is the right one and is worth switching for years to come.
Just giving people an alternative is not enough to convince them.