The OER movement originated and integrated into ODE developments. Mega Universities (MUs) are among the most important of ODE providers worldwide should be to be the primary organizations for providing access to OER. So far, however, in-depth studies on OER developments in the Asian MUs were very limited. This study focuses on the developments, motives, openness, and sustainability of OER at the six MUs official websites in Asia. Data were collected for six months using the documentation techniques and analyzed using web content or textual analyze. Results of the study shown, that: (1) OER developments on the Asian MUs' were an ongoing process, multiyear program, and developed into three characteristics: special projects or initiatives; uploading the existing learning resources collections on the Website; and by taken out-links to the centers of OER websites worldwide. Contents of OER are very rich, diverse in categories, forms, and organized integrally into "One Stop Window". The OER materials have developed by university as well as by joined with various parties of internal and external universities; (2) OER developments are based on three motives: the altruistic motivation of sharing, ego-boost motivation, and combination of both; (3) The OER openness for use or reuse by others can be classified into five categories: openness in the public domain; openness under provision by any license; openness under guarantee by government Laws, policies, missions or visions; openness under guarantee by universities policies, missions or visions; and openness because it was developed as a special initiative of the universities; and (4) Sustainability models that have been used by MUs to makes OER become viable, and stable for the long-term are institutional, governmental, workflow, user-centered, wiki, and social software models.