free basic compilers
The compiler generates 80286 assembly language, which can be assembled and linked using free assemblers and linkers (available from their website). Source code, in BASIC, is provided.
Open source Basic to C translator.
An embeddable and extensible basic interpreter. Made to be embedded in applications to manipulate appliaction's objects and call application's functions. Comes with source code and is free.
Absolute clone of Microsoft Visual Basic.

PowerBasic is a compiler, not an interpreter, for Basic programming language. This shareware compiler provides many new features, and is suitable for beginners.
This is the free QuickBasic development environment and compiler from Microsoft Corporation. In this new version of QuickBasic you can make EXE files. It includes a very good help, better than in the previous version, where you can reference through any qbasic commands or statements. Help also includes example programs on each command or statement.