Lazarus is the class libraries for Free Pascal that emulate Delphi.
Free Pascal is a GPL'ed compiler that runs on Linux, Win32, OS/2, 68K
and more. Free Pascal is designed to be able to understand and compile
Delphi syntax, which is of course OOP.

Lazarus is the part of the missing puzzle that will allow you to
develop Delphi-like programs in all of the above platforms. Unlike Java
which strives to be a write once run anywhere, Lazarus and Free Pascal
strives for write once compile anywhere.

WWW: https://www.lazarus-ide.org/