There are few things more frustrating for fans than knowing something excellent exists but having no way to (legally) see it. At least in the case of Legend of the Galactic Heroes, Sentai Filmworks has good news.
Legend of the Galactic Heroes started as a series of ten novels by Yoshiki Tanaka (slated for their own release here starting in Spring of 2016) and then became a sprawling series of animated films and episodes. The main series was 110 episodes made over ten years, for example.
There’s a tyrannical Galactic Empire and a rebellion — the Free Planets Alliance — which have been at war for 150 years before the anime starts. Something that complicated and large is likely what kept it from being distributed for so long.
Put this down as the chance of having a chance to get it, though: there’s no information about when or how it will be released.