I found this on the BU website. They'll take letters from LSDAS.
Letters of Recommendation
If you are applying on-line, you may download the recommendation forms; if you received a printed Bulletin, you will find recommendation forms in the Application section.You should ask each recommender to enclose the recommendation form and letter in an envelope (provided in the Bulletin), seal the envelope, sign it across the seal, and return it to you to be submitted, unopened with other supplemental material. (If the recommender prefers, the letter may be sent directly to the School of Law.) The following recommendations are required:
The certification of a dean or administrative officer in charge of students at the degree-granting undergraduate college or university. We anticipate that in many cases the dean will not know the applicant personally and will base his or her recommendation on information in the applicant’s records. In conformity with licensing standards, the issue of a disciplinary record (or absence of one) must be directly and explicitly addressed in writing. If it is not the policy of the institution to report on disciplinary action, a statement to that effect will be sufficient.
Two additional letters of recommendation:
At least one of these letters should come from someone who has taught the applicant in a substantive college or postgraduate course. If the undergraduate college has a prelaw committee that writes combined appraisals, it may be substituted for the two additional letters of recommendation, clearly indicating the plan to do so. The Admissions Committee values letters from persons who are able to provide a thoughtful, thorough, and candid assessment of an applicant’s academic ability and potential for success in law study. Federal legislation gives each applicant an absolute right of access to his or her recommendations. The applicant may waive this right if he or she so desires, but such a waiver may not be required as a condition for admission to, receipt of financial aid from, or receipt of any other service or benefits from the Boston University School of Law. In addition, Boston University School of Law will also accept letters of recommendation through the LSAC letter of recommendation service that is part of the LSDAS Registration subscription. Your letters will be copied and sent to us along with your LSDAS Report. To use this service, follow the directions for submitting letters outlined in the LSAT/LSDAS Registration and Information Book.