If you are fine with COM and staying with Windows only, Free Pascal has native support for COM interfaces and Lazarus can generate wrapper units for ActiveX controls so that you can use them in a form like anything else.
However i think it might be a better idea to just use a plain old C interface (c2pas can help to automate this if you want to create a hybrid C and Free Pascal project).
I really miss those millenial usenet discussions about whether if you should be trying to send large amounts of data over flaky 56kbps connections (at best) via TCP instead of using CORBA2 because it was slow and required code to adapt existing systems. Delphi already had remote objects, data providers (served via SOAP) and database connections and they actually worked well. In the meantime, microsoft and yahoo invented their own binary chat protocols which worked reliably and scaled to hundreds of thousands of users and everyone was jealous.
The top comment was about C++ support. With LoadLibrary you can easily interface with C functions but not with C++ classes. That's why a lot of C++ code still exposes a C interface if it's used from another language. COM works too but that adds other problems.
