All programs on this site have GPL_License, latest edition. Some of these programs have several versions. The content from TIJ is quoted in the first placed it is used.
In making these programs, I used the OpenJDK compiler and KWrite text editor (for C/C++, I used gcc/g++). For a graphical interface, try Eclipse or NetBeans (for C/C++ try CodeBlocks). See the official Java_Documentation page and the Java_Tutorials from Oracle.
See my Google_Developer_Profile.