Congratulations with 15 years of Open CASCADE availability!
Matra Datavision published Open CASCADE on December 7, 1999. The archives on this forums seem gone, so I could only find external links like this - https://lists.debian.org/debian-devel/1999/12/msg00485.html
Many thanks to the original and current product team, customers and users community and anyone else involved into the project!
Keep up the good work!