Can I take an Irish Studies course (Irish language, history, literature) if I'm not a student at Boston College?
Anyone can study at Boston College on a course-by-course basis. First, you must register as a special student through the Woods College of Advancing Studies (BC's part-time evening college). At that point you may enroll in a regular daytime undergraduate course with the permission of the instructor, providing you have completed any prerequisites. A list of Irish Studies courses is available here.
That being said, single courses at BC run upwards of $3000 per course. They are extremely academically rigorous and require a huge commitment of time and effort. For someone who, for example, wants to study Irish language (sometimes called Gaelic), there are many programs in the Boston area that would be geared toward conversational fluency instead of preparing for graduate work in Irish language. The Irish Cultural Center in Canton, Massachusetts, holds courses in Irish language as well as music and dance, as does the Boston chapter of Cumann na Gaeilge.