Brian,
If you are in the US it is an MLB policy. From their site;
Due to Major League Baseball exclusivities, during the MLB Postseason, all live games will be blacked out in the United States (including the territories of Guam and the U.S. Virgin Islands) and Canada. If you are an MLB.TV Premium Subscriber outside of the United States and Canada, each of these games will be available as an archived game as soon as possible after the conclusion of the applicable game. If you are an MLB.TV Premium Subscriber within the United States or Canada or an MLB.TV subscriber in any territory, each of these games will be available as an archived game approximately 90 minutes after the conclusion of the applicable game.
Doesn't explain how you get it on computer unless there is a proxy?
Jules