Opal should be cited as:
Travis Wheeler and John Kececioglu,
Sure.
Feel free to use them in any way you see fit, with
proper reference to the source.
I'm thinking Java isn't as slow as you probably think it is.
In fact, I think a Java program that avoids over-use of objects
can run just about as fast as an algorithmically identical C program.
See my further explanation.
Terms of use are given here
"Multiple alignment by aligning alignments,"
Proceedings of the 15th ISCB Conference on Intelligent Systems for Molecular Biology, Bioinformatics 23, i559-i568, 2007.