What kind of linear regression? For something simple like least squares, I’d just program it myself:
http://mathworld.wolfram.com/LeastSquaresFitting.html
The math is not too hard to follow there, give it a shot for an hour or so and let me know if it’s too hard, I can try it.
EDIT:
Found someone that did it:
http://dracoblue.net/dev/linear-least-squares-in-javascript/159/