It could only mean that if it were hyphenated. Given that "Open-Source" is hyphenated, one can assume that hyphens have been made explicit, not left implied, and hence this title does not contain that ambiguity.

The title of the submission was changed after my initial comment. The original title was "Mathematics Free Open Source Textbooks", which I interpreted as "textbooks without mathematics that are open source." My initial comment was intended to clarify the content on the submission for people reading the comments.