True BASIC is an implementation of BASIC. Other implementations of BASIC.
True BASIC is the commercial version of the original BASIC by Kemeny and Kurtz. True BASIC formerly supported a few different platforms, but recent versions require Windows.
True BASIC started out as an ANSI BASIC-compliant compiler, with enhancements soon added to extend the functionality. The code is somewhat similar to old Microsoft BASIC code (i.e. BASICA and GW-BASIC), but is dissimilar enough that it requires translation. The True BASIC website offers a free "BASIC-to-True BASIC" converter to ease the process (and also a Fortran-to-True BASIC converter).
Rosetta Code seems to have no True BASIC-specific solutions.