One of the defining features of Super Mario Maker on the Wii U is the ability to share your creations with the world via the internet. The recently released 3DS version lacks online sharing for some stupid reason, so the homebrew scene is working to do what Nintendo didn't. They're getting there.
Released last week, Super Mario Maker 3DS boasts many of the same features as its console cousin, but falls flat when it comes to the community features that make the Wii U version so compelling. Rather than being able to upload their creations to an official community, joining the millions of levels already crafted by console players, 3DS users are limited to sharing locally with friends or randomly with nearby strangers using the handheld's Streetpass feature. 3DS players cannot access those millions of community creations either, instead limited to a handful of popular levels curated by Nintendo.
Modder MarcusD over at the GBATemp forums (via Wololo) is looking to bring sharing back with OCDM (Online Course Database Manager), a homebrew application that aims allow users to export their 3DS saves to an SD card, restore their own (or other users') save files and maintain an online database of created content.
The current version of OCDM allows save files to be backed up and converted for use in the Wii U version of the game, allowing levels created on the 3DS to be shared with the community at large. The ability to import saves to the 3DS version and online database functionality should be implemented shortly, with plans for a graphical user interface showing thumbnails of created levels and converting Wii U saves to 3DS being looked into.
This being an unofficial solution, players will have to have a homebrew launcher installed on their 3DS in order to allow OCDM to run, which can be a tricky operation requiring specific games running on specific 3DS firmware versions, but at least it exists.
While I can see how Nintendo might want to protect the integrity and safety of the 3DS online environment, releasing a game like Super Mario Marker on the platform without a key feature that made the game so attractive in the first place is just ridiculous. Good on Marcus D for trying to make it suck a little less.