I was recently accepted into the MALS program and want to make a clear distinction between Harvard Extension (or any other 'Extension School') and that of the MALS program.
First off: MALS is a recognized department within the Dartmouth Graduate School of Arts and Sciences and the degree is heralded as fully a Dartmouth Masters Degree, rather than the distinction made by Harvard that the degrees are 'Extension School Masters degrees' separate from Harvard College degrees.
Second: MALS offers the grad student to collaborate with professors from all over the college in multiple areas as deemed fit by the chosen MALS course of study. There is no restriction placed on work or research other than the stipulations of various courses for reasons of degree choice sought. Harvard Extension requires that all HES courses be done ONLY at the HES and not that of Harvard College itself, thereby limiting the educational aspects of HES to be quite different and separate from that of Harvard's graduate school. MALS is not separate from the Graduate School of Arts and Sciences. One can see clearly in this link that MALS is listed with all the other Masters degrees offered and is on par with them as far as the College is concerned. http://graduate.dartmouth.edu/programs/index.html
Third: MALS offers funding (scholarships etc) for qualified applicants as it does for all Masters programs. Students are provided housing as well as full access to all facilities and benefits of the Graduate School.
MALS students are offered summer programs at Oxford University... need I say more...
After looking around at both domestic and and foreign universities in the UK, It appears that the MALS program attempts to model itself much after the European model of research masters degrees. The European model is more student directed and research based, fostering more of an independent and interdisciplinary yet focused approach to studies. MALS gives the USA student an opportunity (at an Ivy League) to do so in a similar manner while still having the taught elements to satisfy a domestic Masters Degree.