One of VB's selling points was that you could call COM components written in C/C++, even if they weren't designed for VB. However, the opposite is also true. VB could create COM servers that could be used by any COM aware code. It was kind of gross integrating a VB component into a C/C++ application, but also kind of amazing that it worked.
I sold COM components written in VB6 as a relatively new grad, and still remember my first support issue for someone who was consuming in C++. It was stressful and the solution ugly but we got it working!
How is RAD Basic guaranteeing 100% VB6 compatibility _including_ COM components? You'd probably want a 32-bit Windows OS to execute that native code correctly. Are they doing some sort of emulation here or is it just completely not covered?
32bit COM should work fine in 64bit Windows since it can run 32bit software - even classic VB. Obviously that would require a 32bit runtime. For a 64bit runtime they'd need either a 64bit version or only able to load 32bit out of process COM servers. AFAIK most COM stuff for VB was in-process (e.g. ActiveX controls) so those might be a problem but perhaps some sort of "32bit-to-64bit" bridge (via a separate 32bit process that communicates with the 64bit runtime) would work for the most part.
I think a harder part would be libraries/COM/extensions/whatever that access/modify the VB6 runtime internals.
