This language tool is a resurrection of code developed at Eindhoven University in 1993 or thereabouts. Its roots go back even further e.g. a program to generate railroad diagrams for grammars was developed in the late 1980s.
The original program was written in Pascal and ran on Apollo Domain workstations and later Hewlett-Packard HP9000 minicomputers. The resurrection merely consisted of porting the dialect of Pascal to Free Pascal. This way it now compiles and runs on many modern architectures.
An LL(1) checker is a formal language tool that checks whether a given grammar complies with the LL(1) condition. This means that the grammar must not be left-recursive and that in all cases at most 1 token look-ahead suffices to decide which production rule applies for a particular non-terminal occurrence on the right-hand side of a rule. (The program actually checks for the so-called strong LL(1) condition, which stipulates that any input seen so far is irrelevant to the decision).
The grammar is specified in a very flexible Domain Specific Language (DSL) dubbed SBNF which stands for Super Backus-Naur Form. John Backus and Peter Naur were the authors of the report on Algol 60 where the use of a formal notation for syntax description was first introduced.
[1] "Syntax of Programming Languages: Theory and Practice," R. Backhouse, Prentice-Hall International, 1979