A Logic-Based Concurrent Object-Oriented Programming Language Article Rafael Ramirez. http://citeseer.ist.psu.edu/rd/46765635%2C157428%2C1%2C0.25%2CDownload/http://citeseer.ist.psu.edu/cache/papers/cs/3588/http:zSzzSzwww.cs.bris.ac.ukzSzToolszSzReportszSzPszSz1996-ramirez.pdf/melendez97logicbased.pdf

Tempo: a declarative concurrent programming language Based on classical first-order logic; improves on usual concurrent logic languages (eg, Parlog) by explicitly specifying aspects of behavior of concurrent programs, namely: safety properties; gives advantages in writing concurrent programs and manipulating them while preserving correctness. http://citeseer.ist.psu.edu/rd/46765635%2C519806%2C1%2C0.25%2CDownload/http://citeseer.ist.psu.edu/cache/papers/cs/21257/http:zSzzSzwww.cs.bris.ac.ukzSz%7EstevezSzresearchzSzpaperszSztempo.pdf/gregory95tempo.pdf

Squirrel A high level imperative/OO programming language, designed to be a scripting tool that fits in the size, memory bandwidth, and real-time requirements of applications like games. [Open source, zlib/libpng licence] http://squirrel.sourceforge.net/