First of all do note
this as original author abandoned the project for ages now.
Secondly, if there is any chance that it will not compile with fpc compiler then you can be rest assured that developers will address that when when you mention that to them. FPC is about compatibility and although sometimes things do break, it has always been addressed. Delphi compatibility is one of the priorities of the development team.
Note that there are many other projects out there that could be considered "dated". Why change a winning horse when it works as expected ? Having a project dated 2018, does not automatically means it is better than a project dated 2000