I just noticed that "foreword" is surprisingly often miswritten "forward," even in cite-checked and edited law review articles.
One data point: The Harvard Law Review's yearly Supreme Court issue contains "Foreword" articles, which are almost always by top legal scholars and often end up being heavily cited. They are also generally labeled "The Supreme Court, [year] Term: Foreword -- [Title]." Searching for "Term Foreword" pre/20 "Harv. L. Rev." and date(> 1/1/2000) through the LAWREV;ALLREV file in Lexis reveals 1795 citing articles. But running the same search for "Term Forward" ... reveals 179, with virtually no false positives. That's a much higher error rate than I would have expected.
Of course, one day "forward" might become common enough to be a perfectly acceptable synonym for "foreword." (I hope not, but it might happen; many perfectly acceptable words today were once errors.) But this day hasn't yet come, and certainly the dictionaries don't suggest that it has come. Plus in any event, when you're citing a document with "Foreword" in its title, "Foreword" is what you should use. So be careful out there.