If I develop on Windows 64 bit can I port to a Linux 64 bit machine.
The question is not very clear. If you want to develop an application on Windows 64 bit which uses CUBRID Databases to store some data, then want that application to work on Linux, you can do so. There is no difference between Windows and Linux versions. They are compatible.
You simply install Linux version of CUBRID on Linux, Windows version on Windows. When you are done with the development on Windows, you simply unloaddb the database from Windows version, then loaddb that database to Linux version. You can check out this Migrating Database manual page.
If you have other questions, please create a separate questions, or simply comment under this answer.
You are either using a very old browser or a browser that is not supported. In order to browse cubrid.org you need to have one of the following browsers: