IGES is an old US military standard. It means 'Initial Graphics Exchange
Specification'
and the specification for it is freely available, since it's a work from
a US government
agency (I got it ;-). As the name says, it was meant as preliminary
work, but served
it's purpose for decades. Now it's being replaced by STEP...
For the reason that STEP costs a lot of money, I wonder how the FreeCAD
guys
want to keep the promisse to provide import and export for it - maybe a
feature
of the OpenCASCADE kernel - but how did they?